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arxiv_dataset-200708.2149 | When do stepwise algorithms meet subset selection criteria?
math.ST stat.TH
Recent results in homotopy and solution paths demonstrate that certain
well-designed greedy algorithms, with a range of values of the algorithmic
parameter, can provide solution paths to a sequence of convex optimization
problems. On the other hand, in regression many existing criteria in subset
selection (including $C_p$, AIC, BIC, MDL, RIC, etc.) involve optimizing an
objective function that contains a counting measure. The two optimization
problems are formulated as (P1) and (P0) in the present paper. The latter is
generally combinatoric and has been proven to be NP-hard. We study the
conditions under which the two optimization problems have common solutions.
Hence, in these situations a stepwise algorithm can be used to solve the
seemingly unsolvable problem. Our main result is motivated by recent work in
sparse representation, while two others emerge from different angles: a direct
analysis of sufficiency and necessity and a condition on the mostly correlated
covariates. An extreme example connected with least angle regression is of
independent interest.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-201708.2249 | The spin structure of the pion
hep-lat hep-ph
We present the first calculation of the transverse spin structure of the pion
in lattice QCD. Our simulations are based on two flavors of non-perturbatively
improved Wilson fermions, with pion masses as low as 400 MeV in volumes up to
(2.1 fm)^3 and lattice spacings below 0.1 fm. We find a characteristic
asymmetry in the spatial distribution of transversely polarized quarks. This
asymmetry is very similar in magnitude to the analogous asymmetry we previously
obtained for quarks in the nucleon. Our results support the hypothesis that all
Boer-Mulders functions are alike.
| arxiv topic:hep-lat hep-ph |
arxiv_dataset-202708.2349 | Non-intersecting paths and Hahn orthogonal polynomial ensemble
math.PR math-ph math.CO math.MP
We compute the bulk limit of the correlation functions for the uniform
measure on lozenge tilings of a hexagon. The limiting determinantal process is
a translation invariant extension of the discrete sine process, which also
describes the ergodic Gibbs measure of an appropriate slope.
| arxiv topic:math.PR math-ph math.CO math.MP |
arxiv_dataset-203708.2449 | The Local Velocity Anomaly
astro-ph
There is a velocity discontinuity at about 7 Mpc between the galaxies of the
Local Sheet that are moving together with low internal velocity dispersion and
the adjacent structures. The Local Sheet bounds the Local Void. The Local Sheet
is determined to have a peculiar velocity of 260 km/s away from the center of
the void. In order for this large velocity to be generated by an absence of
gravity, the Local Void must be at least 45 Mpc in diameter and be very empty.
| arxiv topic:astro-ph |
arxiv_dataset-204708.2549 | The scalar curvature flow in Lorentzian manifolds
math.DG
We prove the existence of closed hypersurfaces of prescribed scalar curvature
in globally hyperbolic Lorentzian manifolds provided there are barriers.
| arxiv topic:math.DG |
arxiv_dataset-205708.2649 | Quantization of neutron in Earth's gravity
hep-th quant-ph
Gravity is the weakest of all four known forces in the universe. Quantum
states of an elementary particle due to such a weak field is certainly very
shallow and would therefore be an experimental challenge to detect. Recently an
experimental attempt was made by V. V. Nesvizhevsky et al., Nature 415, 297
(2002), to measure the quantum states of a neutron, which shows that ground
state and few excited states are \sim 10^{-12}eV. We show that the energy of
the ground state of a neutron confined above Earth's surface should be \sim
10^{-37}eV. The experimentally observed energy levels are 10^{25} times deeper
than the actual energy levels it should be and thus certainly not due to
gravitational effect of Earth. Therefore the correct interpretation for the
painstaking experimental results of Ref. \cite{nes1} is due to the confinement
potential of a one dimensional box of length L \sim 50\mu m, generated from the
experimental setup as commented before \cite{hansoon}. Our results thus creates
a new challenge to the experimentalist to resolve the shallow energy levels of
the neutron in Earth's gravitational field in future.
| arxiv topic:hep-th quant-ph |
arxiv_dataset-206708.2749 | The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary
astro-ph
The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year
project to identify and measure light curves for intermediate-redshift (0.05 <
z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging
over an area of 300 sq. deg. The survey region is a stripe 2.5 degrees wide
centered on the celestial equator in the Southern Galactic Cap that has been
imaged numerous times in earlier years, enabling construction of a deep
reference image for discovery of new objects. Supernova imaging observations
are being acquired between 1 September and 30 November of 2005-7. During the
first two seasons, each region was imaged on average every five nights.
Spectroscopic follow-up observations to determine supernova type and redshift
are carried out on a large number of telescopes. In its first two three-month
seasons, the survey has discovered and measured light curves for 327
spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c,
32 confirmed SNe II, plus a large number of photometrically identified SNe Ia,
94 of which have host-galaxy spectra taken so far. This paper provides an
overview of the project and briefly describes the observations completed during
the first two seasons of operation.
| arxiv topic:astro-ph |
arxiv_dataset-207708.2849 | Orientation Dependence of the Anomalous Hall Resistivity in Single
Crystals of Yb14MnSb11
cond-mat.str-el
The Hall resistivity, electrical resistivity and magnetization of single
crystals of the tetragonal ferromagnet Yb14MnSb11 are reported as a function of
the direction of the current, I, and magnetic field, H with respect to the
principal crystallographic axes. With I along the unique c direction and H in
the a-b plane, the anomalous Hall resistivity in the limit of zero applied
field is negative for all temperatures T less than Tc= 53 K. In this direction,
the anomalous Hall effect behaves in a manner similar to that observed in other
ferromagnets such as Fe, Co, Mn5Ge3, and EuFe4Sb12. However, with I in the a-b
plane and H along the c direction, the anomalous Hall behavior is completely
different. The anomalous Hall resistivity data are positive for all T less than
Tc and a similar analysis of these data fails. In this direction, the anomalous
response is not a simple linear function of the magnetization order parameter,
and for a fixed temperature (T less than Tc) does not depend on the magnitude
of the magnetization perpendicular to the current in the a-b plane. That is,
when the magnetization and applied field are rotated away from the c direction,
the anomalous Hall resistivity does not change. In all other soft ferromagnets
that we have examined (including La doped crystals of Yb14MnSb11, i.e.
Yb13.3La0.7MnSb11) rotation of the magnetization and magnetic field by an angle
theta away from a direction perpendicular to I results in a decrease in both
the anomalous and normal portions of the Hall resistivity that approximately
scales as cos(theta). We suggest that the unique response exhibited by
Yb14MnSb11 is a direct reflection of the delicate balance between
ferromagnetism and Kondo screening.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-208708.2949 | Can Extra Mixing in RGB and AGB Stars Be Attributed to Magnetic
Mechanisms?
astro-ph
It is known that there must be some weak form of transport (called cool
bottom processing, or CBP) acting in low mass RGB and AGB stars, adding nuclei,
newly produced near the hydrogen-burning shell, to the convective envelope. We
assume that this extra-mixing originates in a stellar dynamo operated by the
differential rotation below the envelope, maintaining toroidal magnetic fields
near the hydrogen-burning shell. We use a phenomenological approach to the
buoyancy of magnetic flux tubes, assuming that they induce matter circulation
as needed by CBP models. This establishes requirements on the fields necessary
to transport material from zones where some nuclear burning takes place,
through the radiative layer, and into the convective envelope. Magnetic field
strengths are determined by the transport rates needed by CBP for the model
stellar structure of a star of initially 1.5 solar mass, in both the AGB and
RGB phases. The field required for the AGB star in the processing zone is B_0 ~
5x10^6 G; at the base of the convective envelope this yields an intensity B_E <
10^4 G (approximately). For the RGB case, B_0 ~ 5x10^4 to 4x10^5 G, and the
corresponding B_E are ~ 450 to 3500 G. These results are consistent with
existing observations on AGB stars. They also hint at the basis for high field
sources in some planetary nebulae and the very large fields found in some white
dwarfs. It is concluded that transport by magnetic buoyancy should be
considered as a possible mechanism for extra mixing through the radiative zone,
as is required by both stellar observations and the extensive isotopic data on
circumstellar condensates found in meteorites.
| arxiv topic:astro-ph |
arxiv_dataset-209708.3049 | Photoabsorption in a plasma in a high magnetic field
astro-ph
Photo-absorption in fully ionized plasmas in high magnetic fields is
re-examined, using the methods of many-body quantum field theory. For
frequencies in the immediate vicinity of the electron cyclotron resonance the
rates we obtain disagree markedly from those in the literature. The new element
in our work that causes most of the disagreement is the inclusion of the lowest
order real part of the energy-shift of the resonant state, where, in effect,
previous authors had included only the imaginary part. In a region around and
below the proton cyclotron resonance our results also disagree with those of
previous authors, for a number of reasons.
| arxiv topic:astro-ph |
arxiv_dataset-210708.3149 | Convexity of Hypersurfaces in Spherical Spaces
math.MG math.DG
A spherical set is called convex if for every pair of its points there is at
least one minimal geodesic segment that joins these points and lies in the set.
We prove that for n >= 3 a complete locally-convex (topological) immersion of a
connected (n-1)-manifold into the n-sphere is a surjection onto the boundary of
a convex set.
| arxiv topic:math.MG math.DG |
arxiv_dataset-211708.3249 | On the Khovanov and knot Floer homologies of quasi-alternating links
math.GT math.SG
Quasi-alternating links are a natural generalization of alternating links. In
this paper, we show that quasi-alternating links are "homologically thin" for
both Khovanov homology and knot Floer homology. In particular, their bigraded
homology groups are determined by the signature of the link, together with the
Euler characteristic of the respective homology (i.e. the Jones or the
Alexander polynomial). The proofs use the exact triangles relating the homology
of a link with the homologies of its two resolutions at a crossing.
| arxiv topic:math.GT math.SG |
arxiv_dataset-212708.3349 | Sharp phase transition and critical behaviour in 2D divide and colour
models
math.PR math-ph math.MP
Consider subcritical Bernoulli bond percolation with fixed parameter p<p_c.
We define a dependent site percolation model by the following procedure: for
each bond cluster, we colour all vertices in the cluster black with probability
r and white with probability 1-r, independently of each other. On the square
lattice, defining the critical probabilities for the site model and its dual,
r_c(p) and r_c^*(p) respectively, as usual, we prove that r_c(p)+r_c^*(p)=1 for
all subcritical p. On the triangular lattice, where our method also works, this
leads to r_c(p)=1/2, for all subcritical p. On both lattices, we obtain
exponential decay of cluster sizes below r_c(p), divergence of the mean cluster
size at r_c(p), and continuity of the percolation function in r on [0,1]. We
also discuss possible extensions of our results, and formulate some natural
conjectures. Our methods rely on duality considerations and on recent
extensions of the classical RSW theorem.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-213708.3449 | On Local Behavior of Holomorphic Functions Along Complex Submanifolds of
C^N
math.CV math.FA
In this paper we establish some general results on local behavior of
holomorphic functions along complex submanifolds of $\Co^{N}$. As a corollary,
we present multi-dimensional generalizations of an important result of Coman
and Poletsky on Bernstein type inequalities on transcendental curves in
$\Co^{2}$.
| arxiv topic:math.CV math.FA |
arxiv_dataset-214708.3549 | Lopsidedness and Sloshing in Centres of Advanced Mergers of Galaxies
astro-ph
We measure the non-axisymmetry in the luminosity distribution in the central
few kpc of a sample of advanced mergers of galaxies, by analyzing their 2MASS
images. All mergers show a high central asymmetry: the centres of isophotes
show a striking sloshing pattern with a spatial variation of upto 30 % within
the central 1 kpc; and the Fourier amplitude for lopsidedness (m=1) shows high
values upto 0.2 within the central 5 kpc. The central asymmetry is estimated to
be long-lived, lasting for ~ a few Gyr or ~ 100 local dynamical timescales.
This will significantly affect the dynamical evolution of this region, by
helping fuel the central active galactic nucleus, and also by causing the
secular growth of the bulge driven by lopsidedness.
| arxiv topic:astro-ph |
arxiv_dataset-215708.3649 | Relationship Between Bicomplex Generalized Analytic Functions and
Solutions of the Complexified Schr\"odinger Equation
math.CV
Using three different representations of the bicomplex numbers $T\cong
Cl_{C}(1,0) \cong Cl_{C}(0,1)$, which is a commutative ring with zero divisors
defined by $T={w_0+w_1 {i_1}+w_2{i_2}+w_3 {j} | w_0,w_1,w_2,w_3 \in{R}}$ where
${i_1^{2}}=-1, {i_2^{2}}=-1, {j^{2}}=1 and {i_1}{i_2}={j}={i_2}{i_1}$, we
construct three classes of bicomplex pseudoanalytic functions. In particular,
we obtain some specific systems of Vekua equations of two complex variables and
we established some connections between one of these systems and the classical
Vekua equations. We consider also the complexification of the real stationary
two-dimensional Schr{\"o}dinger equation. With the aid of any of its particular
solutions, we construct a specific bicomplex Vekua equation possessing the
following special property. The scalar parts of its solutions are solutions of
the original complexified Schr{\"o}dinger equation and the vectorial parts are
solutions of another complexified Schr{\"o}dinger equation.
| arxiv topic:math.CV |
arxiv_dataset-216708.3749 | Berry's phase
quant-ph
Berry's phase, entry in the Compendium of Quantum Physics: Concepts,
Experiments, History and Philosophy, ed. F. Weinert, K. Hentschel, D.
Greenberger and B. Falkenburg (Springer), to appear
| arxiv topic:quant-ph |
arxiv_dataset-217708.3849 | How much of the inflaton potential do we see?
astro-ph gr-qc
We discuss the latest constraints on a Taylor-expanded scalar inflaton
potential, obtained focusing on its observable part only. This is in contrast
with other works in which an extrapolation of the potential is applied using
the slow-roll hierarchy. We find significant differences. The results discussed
here apply to a broader range of models, since no assumption about the
invisible e-folds of inflation has to be made, thereby remaining conservative.
| arxiv topic:astro-ph gr-qc |
arxiv_dataset-218708.3949 | Categorification of Wedderburn's basis for \mathbb{C}[S_n]
math.RT math.GR
M. Neunh{\"o}ffer studies in \cite{Ne} a certain basis of $\mathbb{C}[S_n]$
with the origins in \cite{Lu} and shows that this basis is in fact Wedderburn's
basis. In particular, in this basis the right regular representation of $S_n$
decomposes into a direct sum of irreducible representations (i.e. Specht or
cell modules). In the present paper we rediscover essentially the same basis
with a categorical origin coming from projective-injective modules in certain
subcategories of the BGG-category $\mathcal{O}$. An important role in our
arguments is played by the dominant projective module in each of these
categories. As a biproduct of the study of this dominant projective module we
show that {\it Kostant's problem} (\cite{Jo}) has a negative answer for some
simple highest weight module over the Lie algebra $\mathfrak{sl}_4$, which
disproves the general belief that Kostant's problem should have a positive
answer for all simple highest weight modules in type $A$.
| arxiv topic:math.RT math.GR |
arxiv_dataset-219708.4049 | An analysis of the durations of Swift Gamma-Ray Bursts
astro-ph
We report the systematic analysis of the durations for Swift gamma-ray bursts
(GRBs) and compare the results with those of pre-Swift data. For 95 GRBs with
known redshift, we show that the observed durations have two lognormal
distributions that are clearly divided at $T_{90}\simeq2$ s. This is consistent
with the earlier BATSE results. The intrinsic durations also show a bimodal
distribution but shift systematically toward the smaller value and the
distribution exhibits a narrower width compared with the observed one. We find
that the intrinsic distributions of long GRBs between Swift and pre-Swift are
significantly different particularly in the width and the median value. In
addition, the Swift data exhibit a wider dynamic range of duration. Our present
study not only confirms the spectra of short GRBs are in general harder than
the long GRBs in the observer frame but also shows this trend becomes weaker in
the source frame.
| arxiv topic:astro-ph |
arxiv_dataset-220708.4149 | On the complexity of nonnegative matrix factorization
cs.NA cs.IR
Nonnegative matrix factorization (NMF) has become a prominent technique for
the analysis of image databases, text databases and other information retrieval
and clustering applications. In this report, we define an exact version of NMF.
Then we establish several results about exact NMF: (1) that it is equivalent to
a problem in polyhedral combinatorics; (2) that it is NP-hard; and (3) that a
polynomial-time local search heuristic exists.
| arxiv topic:cs.NA cs.IR |
arxiv_dataset-221708.4249 | Examples of the Zeroth Theorem of the History of Physics
physics.hist-ph
The zeroth theorem of the history of science (enunciated by E. P. Fischer)
and widely known in the mathematics community as Arnol'd's Principle (decreed
by M. V. Berry), states that a discovery (rule, regularity, insight) named
after someone (often) did not originate with that person. I present five
examples from physics: the Lorentz condition defining the Lorentz gauge of the
electromagnetic potentials; the Dirac delta function (x); the Schumann
resonances of the earth-ionosphere cavity; the Weizsacker-Williams method of
virtual quanta; the BMT equation of spin dynamics. I give illustrated thumbnail
sketches of both the true and reputed discoverers and quote from their
"discovery" publications.
| arxiv topic:physics.hist-ph |
arxiv_dataset-222708.4349 | Detecting unstable periodic spatio-temporal states of spatial extended
chaotic systems
nlin.CD nlin.PS
The method of detection of the unstable periodic spatio-temporal states of
spatial extended chaotic systems has been proposed. The application of this
method is illustrated by the consideration of two different systems: i) the
fluid model of Pierce diode being one of the fundamental system of the physics
of plasmas and microwave electronics and ii) the complex one-dimensional
Ginzburg-Landau equation demonstrating different regimes of spatio-temporal
chaos.
| arxiv topic:nlin.CD nlin.PS |
arxiv_dataset-223709.0035 | On The Limitations of The Naive Lattice Decoding
cs.IT math.IT
In this paper, the inherent drawbacks of the naive lattice decoding for MIMO
fading systems is investigated. We show that using the naive lattice decoding
for MIMO systems has considerable deficiencies in terms of the rate-diversity
trade-off. Unlike the case of maximum-likelihood decoding, in this case, even
the perfect lattice space-time codes which have the non-vanishing determinant
property can not achieve the optimal rate-diversity trade-off. Indeed, we show
that in the case of naive lattice decoding, when we fix the underlying lattice,
all the codes based on full-rate lattices have the same rate-diversity
trade-off as V-BLAST. Also, we drive a lower bound on the symbol error
probability of the naive lattice decoding for the fixed-rate MIMO systems (with
equal numbers of receive and transmit antennas). This bound shows that
asymptotically, the naive lattice decoding has an unbounded loss in terms of
the required SNR, compared to the maximum likelihood decoding.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-224709.0135 | An improved solar wind electron-density model for pulsar timing
astro-ph
Variations in the solar wind density introduce variable delays into pulsar
timing observations. Current pulsar timing analysis programs only implement
simple models of the solar wind, which not only limit the timing accuracy, but
can also affect measurements of pulsar rotational, astrometric and orbital
parameters. We describe a new model of the solar wind electron density content
which uses observations from the Wilcox Solar Observatory of the solar magnetic
field. We have implemented this model into the tempo2 pulsar timing package. We
show that this model is more accurate than previous models and that these
corrections are necessary for high precision pulsar timing applications.
| arxiv topic:astro-ph |
arxiv_dataset-225709.0235 | Flavors and Phases in Unparticle Physics
hep-ph
Inspired by the recent Georgi's unparticle proposal, we study the flavor
structures of the standard model (SM) particles when they couple to
unparticles. At a very high energy scale, we introduce $\BZ$ charges for the SM
particles, which are universal for each generation and allow $\BZ$ fields to
distinguish flavor generations. At the $\Lambda_{\UP}$ scale, $\BZ$ operators
and charges are matched onto unparticle operators and charges, respectively. In
this scenario, we find that tree flavor changing neutral currents (FCNCs) can
be induced by the rediagonalizations of the SM fermions. As an illustration, we
employ the Fritzsch ansatz to the SM fermion mass matrices and we find that the
FCNC effects could be simplified to be associated with the mass ratios denoted
by $\sqrt{m_{i}m_{j}/m^2_{3}}$, where $m_3$ is the mass of the heaviest
particle in each type of fermion generations and $i, j$ are the flavor indices.
In addition, we show that there is no new CP violating phase beside the unique
one in the CKM matrix. We use $\bar B_{q}\to \ell^{+} \ell^{-}$ as examples to
display the new FCNC effects. In particular, we demonstrate that the direct CP
asymmetries in the decays can be $O(10%)$ due to the peculiar CP conserving
phase in the unparticle propagator.
| arxiv topic:hep-ph |
arxiv_dataset-226709.0335 | Leptonic Decays of the W-Boson in a Strong Electromagnetic Field
hep-ph
The probability of W-boson decay into a lepton and a neutrino in a strong
electromagnetic field is calculated. On the basis of the method for deriving
exact solutions to relativistic wave equations for charged particles, an exact
analytic expression is obtained for the partial W-decay width at an arbitrary
value of the external field strength. It is found that, in the region of
comparatively weak fields, field-induced corrections to the standard decay
width of the W-boson in a vacuum are about a few percent. In these conditions
at first we observe the decrease of the W-boson partial decay width with the
increase of the external field strength parameter. At absolute minimum the
W-width deviates from the corresponding vacuum value by a factor 0,926. Then
with further augmentation of the background field intensity the W-boson decay
width grows monotonously. In superstrong fields the partial W-width is greater
than the corresponding one in vacuum in a dozen of times.
| arxiv topic:hep-ph |
arxiv_dataset-227709.0435 | A Generic Approach to Coalition Formation
cs.GT
We propose an abstract approach to coalition formation that focuses on simple
merge and split rules transforming partitions of a group of players. We
identify conditions under which every iteration of these rules yields a unique
partition. The main conceptual tool is a specific notion of a stable partition.
The results are parametrized by a preference relation between partitions of a
group of players and naturally apply to coalitional TU-games, hedonic games and
exchange economy games.
| arxiv topic:cs.GT |
arxiv_dataset-228709.0535 | Constructing packings in Grassmannian manifolds via alternating
projection
math.MG
This paper describes a numerical method for finding good packings in
Grassmannian manifolds equipped with various metrics. This investigation also
encompasses packing in projective spaces. In each case, producing a good
packing is equivalent to constructing a matrix that has certain structural and
spectral properties. By alternately enforcing the structural condition and then
the spectral condition, it is often possible to reach a matrix that satisfies
both. One may then extract a packing from this matrix.
This approach is both powerful and versatile. In cases where experiments have
been performed, the alternating projection method yields packings that compete
with the best packings recorded. It also extends to problems that have not been
studied numerically. For example, it can be used to produce packings of
subspaces in real and complex Grassmannian spaces equipped with the
Fubini--Study distance; these packings are valuable in wireless communications.
One can prove that some of the novel configurations constructed by the
algorithm have packing diameters that are nearly optimal.
| arxiv topic:math.MG |
arxiv_dataset-229709.0635 | Poisson Sigma Model with branes and hyperelliptic Riemann surfaces
math-ph hep-th math.CV math.MP
We derive the explicit form of the superpropagators in presence of general
boundary conditions (coisotropic branes) for the Poisson Sigma Model. This
generalizes the results presented in Cattaneo and Felder's previous works for
the Kontsevich angle function used in the deformation quantization program of
Poisson manifolds without branes or with at most two branes. The relevant
superpropagators for n branes are defined as gauge fixed homotopy operators of
a complex of differential forms on n sided polygons P_n with particular
"alternating" boundary conditions.
In presence of more than three branes we use first order Riemann theta
functions with odd singular characteristics on the Jacobian variety of a
hyperelliptic Riemann surface (canonical setting). In genus g the
superpropagators present g zero modes contributions.
| arxiv topic:math-ph hep-th math.CV math.MP |
arxiv_dataset-230709.0735 | Magnetogenesis from Rotating Cosmic String Loops
astro-ph hep-th
We present a mechanism to create vortices in a plasma via gravitational
dragging behind rotating cosmic string loops. The vortical motions create
magnetic fields by means of the Harrison-Rees mechanism; the fields are further
enhanced through galactic collapse and dynamo amplification. Employing the
Velocity dependent One Scale model (VOS) for the string network and
incorporating loop dynamics, we compute the magnetic fields generated around
the time of decoupling: these are just strong and coherent enough to account
for presently observed magnetic fields in spiral galaxies if efficient dynamos
with $\Gamma_{dy}^{-1}\approx 0.3$ Gyr are present.
| arxiv topic:astro-ph hep-th |
arxiv_dataset-231709.0835 | Electromagnetic form factors of the Delta(1232) in Dual-Large N_c QCD
hep-ph
The three electromagnetic form factors of the $\Delta(1232)$ resonance,
$G^*_M(q^2)$, $G^*_E(q^2)$, and $G^*_C(q^2)$ are obtained in the space-like
region using a Dual Resonance Model realization of QCD in the large $N_c$ limit
(Dual-${QCD}_{\infty}$). Each form factor involves a single free parameter
which is fixed by fitting data on $G^*_M(q^2)$, and on the ratios $R_{EM}(q^2)$
and $R_{SM}(q^2)$. Good agreement with experiment is obtained for all three
quantities. Results are then used to predict the $q^2$-dependence of the chiral
effective-field theory form factors $g_M(q^2)$, $g_E(q^2)$, and $g_C(q^2)$.
| arxiv topic:hep-ph |
arxiv_dataset-232709.0935 | The Algebraic Complexity of Maximum Likelihood Estimation for Bivariate
Missing Data
math.ST math.AG stat.CO stat.TH
We study the problem of maximum likelihood estimation for general patterns of
bivariate missing data for normal and multinomial random variables, under the
assumption that the data is missing at random (MAR). For normal data, the score
equations have nine complex solutions, at least one of which is real and
statistically significant. Our computations suggest that the number of real
solutions is related to whether or not the MAR assumption is satisfied. In the
multinomial case, all solutions to the score equations are real and the number
of real solutions grows exponentially in the number of states of the underlying
random variables, though there is always precisely one statistically
significant local maxima.
| arxiv topic:math.ST math.AG stat.CO stat.TH |
arxiv_dataset-233709.1035 | Scaling and aging in the homogeneous cooling state of a granular fluid
of hard particles
cond-mat.stat-mech
The presence of the aging phenomenon in the homogeneous cooling state (HCS)
of a granular fluid composed of inelastic hard spheres or disks is
investigated. As a consequence of the scaling property of the $N$-particle
distribution function, it is obtained that the decay of the normalized two-time
correlation functions slows down as the time elapsed since the beginning of the
measurement increases. This result is confirmed by molecular dynamics
simulations for the particular case of the total energy of the system. The
agreement is also quantitative in the low density limit, for which an explicit
analytical form of the time correlation function has been derived. The reported
results also provide support for the existence of the HCS as a solution of the
N-particle Liouville equation.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-234709.1135 | Parameter estimation in diagonalizable bilinear stochastic parabolic
equations
math.PR math.ST stat.TH
A parameter estimation problem is considered for a stochastic parabolic
equation with multiplicative noise under the assumption that the equation can
be reduced to an infinite system of uncoupled diffusion processes. From the
point of view of classical statistics, this problem turns out to be singular
not only for the original infinite-dimensional system but also for most
finite-dimensional projections. This singularity can be exploited to improve
the rate of convergence of traditional estimators as well as to construct
completely new closed-form exact estimator.
| arxiv topic:math.PR math.ST stat.TH |
arxiv_dataset-235709.1235 | Monotonicity for entrywise functions of matrices
math.FA
We characterize real functions $f$ on an interval $(-\alpha,\alpha)$ for
which the entrywise matrix function $[a_{ij}] \mapsto [f(a_{ij})]$ is positive,
monotone and convex, respectively, in the positive semidefiniteness order.
Fractional power functions are exemplified and related weak majorizations are
shown.
| arxiv topic:math.FA |
arxiv_dataset-236709.1335 | Interference of Spontaneous Emission of Light from two Solid-State
Atomic Ensembles
quant-ph
We report an interference experiment of spontaneous emission of light from
two distant solid-state ensembles of atoms that are coherently excited by a
short laser pulse. The ensembles are Erbium ions doped into two LiNbO3 crystals
with channel waveguides, which are placed in the two arms of a Mach-Zehnder
interferometer. The light that is spontaneously emitted after the excitation
pulse shows first-order interference. By a strong collective enhancement of the
emission, the atoms behave as ideal two-level quantum systems and no which-path
information is left in the atomic ensembles after emission of a photon. This
results in a high fringe visibility of 95%, which implies that the observed
spontaneous emission is highly coherent.
| arxiv topic:quant-ph |
arxiv_dataset-237709.1435 | Composition operators in the Lipschitz Space of the Polydiscs
math.FA math.CV
In 1987, Shapiro shew that composition operator induced by symbol $\phi$ is
compact on the Lipschltz space if and only if the infinity norm of $\phi$ is
less than 1 by a spectral-theoretic argument, where $\phi$ is a holomorphic
self-map of the unit disk. In this paper, we shall generalize Shapiro's result
to the $n$-dimensional case.
| arxiv topic:math.FA math.CV |
arxiv_dataset-238709.1535 | Comments on "The Coronal Heating Paradox" by M.J. Aschwanden, A.
Winebarger, D. Tsiklauri and H. Peter [2007, Astrophys J., 659, 1673]
astro-ph
We point out the priority of our paper (Mahajan et al. 2001, Phys. Plasmas,
8, 1340) over (Aschwanden et al. 2007, Astrophys J., 659, 1673) in introducing
the term "Formation and primary heating of the solar corona" working out
explicit models (theory as well as simulation) for coronal structure formation
and heating. On analyzing the Aschwanden et al. (2007) scenario of coronal
heating process (shifted to the chromospheric heating) we stress, that for
efficient loop formation, the primary upflows of plasma in
chromosphere/transition region should be relatively cold and fast (as opposed
to hot). It is during trapping and accumulation in closed field structures,
that the flows thermalize (due to the dissipation of the short scale flow
energy) leading to a bright and hot coronal structure. The formation and
primary heating of a closed coronal structure (loop at the end) are
simultaneous and a process like the "filling of the empty coronal loop by hot
upflows" is purely speculative and totally unlikely.
| arxiv topic:astro-ph |
arxiv_dataset-239709.1635 | Gaudin functions, and Euler-Poincar\'e characteristics
math.CO
Given two positive integers n,r, we define the Gaudin function of level r to
be quotient of the numerator of the determinant det(1/ ((x_i-y_j)(x_i-ty_j) ...
(x_i-t^r y_j)), i,j=1..n, by the two Vandermonde in x and y. We show that it
can be characterized by specializing the x-variables into the y-variables,
multiplied by powers of t. This allows us to obtain the Gaudin function of
level 1 (due to Korepin and Izergin) as the image of a resultant under the the
Euler-Poincar\'e characteristics of the flag manifold. As a corollary, we
recover a result of Warnaar about the generating function of Macdonald
polynomials.
| arxiv topic:math.CO |
arxiv_dataset-240709.1735 | CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
astro-ph
We describe a uniform all-sky survey of bright blazars, selected primarily by
their flat radio spectra, that is designed to provide a large catalog of likely
gamma-ray AGN. The defined sample has 1625 targets with radio and X-ray
properties similar to those of the EGRET blazars, spread uniformly across the
|b| > 10 deg sky. We also report progress toward optical characterization of
the sample; of objects with known R < 23, 85% have been classified and 81% have
measured redshifts. One goal of this program is to focus attention on the most
interesting (e.g., high redshift, high luminosity, ...) sources for intensive
multiwavelength study during the observations by the Large Area Telescope (LAT)
on GLAST.
| arxiv topic:astro-ph |
arxiv_dataset-241709.1835 | Quantitative 3w-Scanning Thermal Microscopy: Modelling the AC/DC
coupling and the sample heat conduction
cond-mat.mtrl-sci
A way to increase the Scanning Thermal Microscope (SThM) sensitivity in the
harmonic 3w mode is to heat the probe with an AC current sufficiently high to
generate a coupling between the AC and the DC signals. We detail in this paper
how to properly take into account this coupling with a Wollaston-probe SThM. We
also show how to link correctly the thermal conductivity to the thermal
conductance measured by the SThM.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-242709.1935 | Clique-width of unit interval graphs
math.CO
The clique-width is known to be unbounded in the class of unit interval
graphs. In this paper, we show that this is a minimal hereditary class of
unbounded clique-width, i.e., in every hereditary subclass of unit interval
graphs the clique-width is bounded by a constant.
| arxiv topic:math.CO |
arxiv_dataset-243709.2035 | Coexistence of hexatic and isotropic phases in two-dimensional Yukawa
systems
cond-mat.soft cond-mat.stat-mech
We have performed Brownian dynamics simulations on melting of two-dimensional
colloidal crystal in which particles interact with Yukawa potential. The pair
correlation function and bond-orientational correlation function was calculated
in the Yukawa system. An algebraic decay of the bond orientational correlation
function was observed. By ruling out the coexistence region, only a unstable
hexatic phase was found in the Yukawa systems. But our work shows that the
melting of the Yukawa systems is a two-stage melting not consist with the KTHNY
theory and the isotropic liquid and the hexatic phase coexistence region was
found. Also we have studied point defects in two-dimensional Yukawa systems.
| arxiv topic:cond-mat.soft cond-mat.stat-mech |
arxiv_dataset-244709.2135 | Coupling Superconducting Qubits via a Cavity Bus
cond-mat.mes-hall cond-mat.supr-con quant-ph
Superconducting circuits are promising candidates for constructing quantum
bits (qubits) in a quantum computer; single-qubit operations are now routine,
and several examples of two qubit interactions and gates having been
demonstrated. These experiments show that two nearby qubits can be readily
coupled with local interactions. Performing gates between an arbitrary pair of
distant qubits is highly desirable for any quantum computer architecture, but
has not yet been demonstrated. An efficient way to achieve this goal is to
couple the qubits to a quantum bus, which distributes quantum information among
the qubits. Here we show the implementation of such a quantum bus, using
microwave photons confined in a transmission line cavity, to couple two
superconducting qubits on opposite sides of a chip. The interaction is mediated
by the exchange of virtual rather than real photons, avoiding cavity induced
loss. Using fast control of the qubits to switch the coupling effectively on
and off, we demonstrate coherent transfer of quantum states between the qubits.
The cavity is also used to perform multiplexed control and measurement of the
qubit states. This approach can be expanded to more than two qubits, and is an
attractive architecture for quantum information processing on a chip.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con quant-ph |
arxiv_dataset-245709.2235 | Bound diquarks and their Bose-Einstein condensation in strongly coupled
quark matter
hep-ph
We explore the formation of diquark molecules and their Bose-Einstein
condensation (BEC) in the phase diagram of three-flavor quark matter at nonzero
temperature, T, and quark chemical potential, mu. Using a quark model with a
four-fermion interaction, we identify possible diquark excitations as poles of
the microscopically computed diquark propagator. The quark masses are obtained
by solving a dynamical equation for the chiral condensate and are found to
determine the stability of the diquark excitations. The stability of diquark
excitations is investigated in the T-mu plane for different values of the
diquark coupling strength. We find that bound diquark molecules appear at small
quark chemical potentials at intermediate coupling and that BEC of non-strange
diquark molecules occurs if the attractive interaction between quarks is
sufficiently strong.
| arxiv topic:hep-ph |
arxiv_dataset-246709.2335 | Higgs boson in non-minimal models at the LHC
hep-ex
While approaching the start of the data taking at the LHC, ATLAS and CMS
perform studies involving the Higgs boson within non-minimal models besides
Supersymmetric models. Highlights from both experiments are summarized; all
results refer to LHC low luminosity conditions of 10^33 cm^-2 s^-1.
| arxiv topic:hep-ex |
arxiv_dataset-247709.2435 | Generalized second law in modified theory of gravity
gr-qc astro-ph
In the context of modified theory of gravity (f(R) gravity) we try to study
the conditions required for validity of the generalized second law.
| arxiv topic:gr-qc astro-ph |
arxiv_dataset-248709.2535 | Gravitational energy as dark energy: Concordance of cosmological tests
astro-ph gr-qc hep-ph hep-th
We provide preliminary quantitative evidence that a new solution to averaging
the observed inhomogeneous structure of matter in the universe [gr-qc/0702082,
arxiv:0709.0732], may lead to an observationally viable cosmology without
exotic dark energy. We find parameters which simultaneously satisfy three
independent tests: the match to the angular scale of the sound horizon detected
in the cosmic microwave background anisotropy spectrum; the effective comoving
baryon acoustic oscillation scale detected in galaxy clustering statistics; and
type Ia supernova luminosity distances. Independently of the supernova data,
concordance is obtained for a value of the Hubble constant which agrees with
the measurement of the Hubble Key team of Sandage et al [astro-ph/0603647].
Best-fit parameters include a global average Hubble constant H_0 = 61.7
(+1.2/-1.1) km/s/Mpc, a present epoch void volume fraction of f_{v0} = 0.76
(+0.12/-0.09), and an age of the universe of 14.7 (+0.7/-0.5) billion years as
measured by observers in galaxies. The mass ratio of non-baryonic dark matter
to baryonic matter is 3.1 (+2.5/-2.4), computed with a baryon-to-photon ratio
that concords with primordial lithium abundances.
| arxiv topic:astro-ph gr-qc hep-ph hep-th |
arxiv_dataset-249709.2635 | Non-Blocking Signature of very large SOAP Messages
cs.DC
Data transfer and staging services are common components in Grid-based, or
more generally, in service-oriented applications. Security mechanisms play a
central role in such services, especially when they are deployed in sensitive
application fields like e-health. The adoption of WS-Security and related
standards to SOAP-based transfer services is, however, problematic as a
straightforward adoption of SOAP with MTOM introduces considerable
inefficiencies in the signature generation process when large data sets are
involved. This paper proposes a non-blocking, signature generation approach
enabling a stream-like processing with considerable performance enhancements.
| arxiv topic:cs.DC |
arxiv_dataset-250709.2735 | Localization and delocalization in the quantum kicked prime number
rotator
nlin.CD
The quantum kicked prime number rotator (QKPR) is defined as the rotator
whose energy levels are prime numbers. The long time behavior is decided by the
kick period $\tau$ and kick strength $k$. When $\frac{\tau}{2\pi}$ is
irrational, QKPR is localized because of the equidistribution theorem. When
$\frac{\tau}{2\pi}$ is rational, QKPR is localized for small $k$, because the
system seems like a generalized kicked dimer model. We argue for rational
$\frac{\tau}{2\pi}$ QKPR delocalizes for large k.
| arxiv topic:nlin.CD |
arxiv_dataset-251709.2835 | Coronae in the Coronet: A very deep X-ray look into a stellar nursery
astro-ph
In order to study the X-ray properties of young stellar objects (YSOs), we
analyze an exceptionally sensitive Chandra dataset of the Coronet cluster in
the CrA star-forming region, achieving a limiting luminosity of LXmin=5E26
erg/sec for lightly absorbed sources. This dataset represents one of the most
sensitive X-ray observations ever obtained of a star-forming region. The X-ray
data are used to investigate the membership status of tentative members of the
region, to derive plasma temperatures and X-ray luminosities of the YSOs, and
to investigate variability on the timescale of several years. 46 of the 92
X-ray sources in the merged Chandra image can be identified with optical or
near/mid-infrared counterparts. X-ray emission is detected from all of the
previously known optically visible late-type (spectral types G to M) stellar
cluster members, from five of the eight brown dwarf candidates, and from nine
embedded objects ("protostars") with class 0, class I, or flat-spectrum SEDs in
the field of view. While the Herbig Ae/Be stars TY CrA and R CrA, a close
companion of the B9e star HD 176386, and the F0e star T CrA are detected, no
X-ray emission is found from any of the Herbig-Haro (HH) objects or the
protostellar cores without infrared source. We find indications for diffuse
X-ray emission near R CrA / IRS 7. The observed X-ray properties of the Coronet
YSOs are consistent with coronal activity; no soft spectral components hinting
towards X-ray emission from accretion shocks were found. The X-ray emission of
the AeBe stars TY CrA and HD 176386 originates probably from close late-type
companions. The Ae star R Cra shows a peculiar X-ray spectrum and an extremely
hot plasma temperature. Finally, we discuss the differences of the X-ray
properties of YSOs in different evolutionary stages.
| arxiv topic:astro-ph |
arxiv_dataset-252709.2935 | An Extension to an Algebraic Method for Linear Time-Invariant System and
Network Theory: The full AC-Calculus
math.CA cs.SC
Being inspired by phasor analysis in linear circuit theory, and its algebraic
counterpart - the AC-(operational)-calculus for sinusoids developed by W.
Marten and W. Mathis - we define a complex structure on several spaces of
real-valued elementary functions. This is used to algebraize inhomogeneous
linear ordinary differential equations with inhomogenities stemming from these
spaces. Thus we deduce an effective method to calculate particular solutions of
these ODEs in a purely algebraic way.
| arxiv topic:math.CA cs.SC |
arxiv_dataset-253709.3035 | Detecting Higgs bosons in the bb decay channel using forward proton
tagging at the LHC
hep-ph
A detailed study is presented of the search for Higgs bosons in the b-decay
channel in the central exclusive production process at the LHC. We present
results for proton tagging detectors at both 220m and 420m around ATLAS or CMS.
We consider two benchmark scenarios; a Standard Model (SM) Higgs boson and the
m_h^{max} scenario of the Minimal Supersymmetric Standard Model (MSSM).
Detector acceptance, smearing and event trigger strategies are considered. We
find that the SM Higgs will be challenging to observe in the b-jet channel
without improvements to the currently proposed experimental configuration, but
a neutral scalar MSSM Higgs Boson could be observable in the b-jet channel with
a significance of 3 sigma or greater within three years of data taking at all
luminosities between 2 x 10^{33} cm^{-2} s^{-1} and 10^{34} cm^{-2} s^{-1}, and
at 5 sigma or greater after three years in certain scenarios.
| arxiv topic:hep-ph |
arxiv_dataset-254709.3135 | A Kondo lattice antiferromagnet CePd5Al2
cond-mat.str-el cond-mat.mtrl-sci
We report on the electrical resistivity, magnetic susceptibility and
heat-capacity measurements on a new intermetallic compound CePd5Al2,
crystallizing in the ZrNi2Al5-type tetragonal structure, with lattice
parameters a = 4.156 A and c = 14.883 A. The compound presents Kondo lattice
behavior and an easy-plane antiferromagnetic ground state with two magnetic
transitions at 2.9 K and 3.9 K. The Sommerfeld coefficient is estimated as 60
mJ/mol K^2.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-255709.3235 | A one-parameter family of dendriform identities
math.CO
We prove a q-identity in the dendriform dialgebra of colored free
quasi-symmetric functions. For q=1, we recover identities due to Ebrahimi-Fard,
Manchon, and Patras, in particular the noncommutative Bohnenblust-Spitzer
identity.
| arxiv topic:math.CO |
arxiv_dataset-256709.3335 | The quest for three-color entanglement: experimental investigation of
new multipartite quantum correlations
quant-ph physics.optics
We experimentally investigate quadrature correlations between pump, signal,
and idler fields in an above-threshold optical parametric oscillator. We
observe new quantum correlations among the pump and signal or idler beams, as
well as among the pump and a combined quadrature of signal and idler beams. A
further investigation of unforeseen classical noise observed in this system is
presented, which hinders the observation of the recently predicted tripartite
entanglement. In spite of this noise, current results approach the limit
required to demonstrate three-color entanglement.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-257709.3435 | Lepton flavor violating $\mu\to e\gamma$ and $\mu-e$ conversion in
unparticle physics
hep-ph
We have studied lepton flavor violation processes $\mu\to e\gamma$ and
$\mu-e$ conversion in nuclei induced by unparticle. Both ${\rm Br}(\mu\to
e\gamma)$ and $\mu-e$ conversion rate ${\rm CR}(\mu-e,{\rm Nuclei})$ strongly
depend on the scale dimension $d_{\cal U}$ and the unparticle coupling
$\lambda^{ff'}_{\rm K}$(K=V, A, S, P). Present experimental upper bounds on
${\rm Br}(\mu\to e\gamma)$, ${\rm CR}(\mu-e,{\rm Ti})$ and ${\rm CR}(\mu-e,{\rm
Au})$ put stringent constraints on the parameters of unaprticle physics. The
scale dimensions $d_{\cal U}$ around 2 are favored for the unparticle scale
$\Lambda_{\cal U}$ of ${\cal O}(10 {\rm TeV})$ and the unparticle coupling of
${\cal O}(10^{-3})$. ${\rm CR}(\mu-e,{\rm Nuclei})$ is proportional to
$\rm{Z^4_{eff}A^2/Z}$ for the pure vector and scalar couplings between
unparticle and SM fermions, this peculiar atomatic number dependence can be
used to distinguish unparticle from other theoretical models.
| arxiv topic:hep-ph |
arxiv_dataset-258709.3535 | Maximum Likelihood Estimation in Latent Class Models For Contingency
Table Data
stat.ME math.ST stat.TH
Statistical models with latent structure have a history going back to the
1950s and have seen widespread use in the social sciences and, more recently,
in computational biology and in machine learning. Here we study the basic
latent class model proposed originally by the sociologist Paul F. Lazarfeld for
categorical variables, and we explain its geometric structure. We draw
parallels between the statistical and geometric properties of latent class
models and we illustrate geometrically the causes of many problems associated
with maximum likelihood estimation and related statistical inference. In
particular, we focus on issues of non-identifiability and determination of the
model dimension, of maximization of the likelihood function and on the effect
of symmetric data. We illustrate these phenomena with a variety of synthetic
and real-life tables, of different dimension and complexity. Much of the
motivation for this work stems from the "100 Swiss Francs" problem, which we
introduce and describe in detail.
| arxiv topic:stat.ME math.ST stat.TH |
arxiv_dataset-259709.3635 | High redshift FRII radio sources: large-scale X-ray environment
astro-ph
We investigate the properties of the environment around 20 powerful radio
galaxies and quasars at redshifts between 0.45 and 1. Using XMM-Newton and
Chandra observations we probe the spatial distribution and the temperature of
the cluster gas. We find that more than 60 per cent of powerful radio sources
in the redshift range of our sample lie in a cluster of X-ray luminosity
greater than 10^44 erg/s, and all but one of the narrow-line radio galaxies,
for which the emission from the nucleus is obscured by a torus, lie in a
cluster environment. Within the statistical uncertainties we find no
significant difference in the properties of the environment as a function of
the orientation to the line of sight of the radio jet. This is in agreement
with unification schemes. Our results have important implications for cluster
surveys, as clusters around powerful radio sources tend to be excluded from
X-ray and Sunyaev-Zeldovich surveys of galaxy clusters, and thus can introduce
an important bias in the cluster luminosity function. Most of the radio sources
are found close to pressure balance with the environment in which they lie, but
the two low-excitation radio galaxies of the sample are observed to be
under-pressured. This may be the first observational indication for the
presence of non-radiative particles in the lobes of some powerful radio
galaxies. We find that the clusters around radio sources in the redshift range
of our sample have a steeper entropy-temperature relation than local clusters,
and the slope is in agreement with the predictions of self-similar
gravitational heating models for cluster gas infall. This suggests that
selection by AGN finds systems less affected by AGN feedback than the local
average.(Abridged)
| arxiv topic:astro-ph |
arxiv_dataset-260709.3735 | Functorial Cartier duality
math.AG
In this paper we obtain the Cartier duality for k-schemes of commutative
monoids functorially without providing the vector spaces of functions with a
topology, generalizing a result for finite commutative algebraic groups by M.
Demazure and P. Gabriel.
| arxiv topic:math.AG |
arxiv_dataset-261709.3835 | Correlated entanglement distillation and the structure of the set of
undistillable states
quant-ph
We consider entanglement distillation under the assumption that the input
states are allowed to be correlated among each other. We hence replace the
usually considered independent and identically-distributed hypothesis by the
weaker assumption of merely having identical reductions. We find that whether a
state is then distillable or not is only a property of these reductions, and
not of the correlations that are present in the input state. This is shown by
establishing an appealing relation between the set of copy-correlated
undistillable states and the standard set of undistillable states: The former
turns out to be the convex hull of the latter. As an example of the usefulness
of our approach to the study of entanglement distillation, we prove a new
activation result, which generalizes earlier findings: it is shown that for
every entangled state and every positive integer k, there exists a
copy-correlated k-undistillable state such that their tensor product is
single-copy distillable. Finally, the relation of our results to the conjecture
about the existence of bound entangled states with a non-positive partial
transpose is discussed.
| arxiv topic:quant-ph |
arxiv_dataset-262709.3935 | Infrared Divergences from Soft and Collinear Gauge Bosons
hep-ph
I review the Lee-Nauenberg thereom and discuss its inclusion of photons which
are disconnected at the level of the S-matrix but connected at the level of the
cross-section when there are initial and final state charged particles. I then
expose a new set of soft collinear divergences in massless gauge theories which
are omitted in the standard Lee-Nauenberg approach. It seems that highly
questionable assumptions are needed to obtain finite cross-sections.
| arxiv topic:hep-ph |
arxiv_dataset-263709.4035 | Energy Efficient Estimation of Gaussian Sources Over Inhomogeneous
Gaussian MAC Channels
cs.IT math.IT
It has been shown lately the optimality of uncoded transmission in estimating
Gaussian sources over homogeneous/symmetric Gaussian multiple access channels
(MAC) using multiple sensors. It remains, however, unclear whether it still
holds for any arbitrary networks and/or with high channel signal-to-noise ratio
(SNR) and high signal-to-measurement-noise ratio (SMNR). In this paper, we
first provide a joint source and channel coding approach in estimating Gaussian
sources over Gaussian MAC channels, as well as its sufficient and necessary
condition in restoring Gaussian sources with a prescribed distortion value. An
interesting relationship between our proposed joint approach with a more
straightforward separate source and channel coding scheme is then established.
We then formulate constrained power minimization problems and transform them to
relaxed convex geometric programming problems, whose numerical results exhibit
that either separate or uncoded scheme becomes dominant over a linear topology
network. In addition, we prove that the optimal decoding order to minimize the
total transmission powers for both source and channel coding parts is solely
subject to the ranking of MAC channel qualities, and has nothing to do with the
ranking of measurement qualities. Finally, asymptotic results for homogeneous
networks are obtained which not only confirm the existing optimality of the
uncoded approach, but also show that the asymptotic SNR exponents of these
three approaches are all the same. Moreover, the proposed joint approach share
the same asymptotic ratio with respect to high SNR and high SMNR as the uncoded
scheme.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-264709.4135 | Effect of matrix parameters on mesoporous matrix based quantum
computation
cond-mat.mes-hall
We present a solid state implementation of quantum computation, which
improves previously proposed optically driven schemes. Our proposal is based on
vertical arrays of quantum dots embedded in a mesoporous material which can be
fabricated with present technology. We study the feasibility of performing
quantum computation with different mesoporous matrices. We analyse which matrix
materials ensure that each individual stack of quantum dots can be considered
isolated from the rest of the ensemble-a key requirement of our scheme. This
requirement is satisfied for all matrix materials for feasible structure
parameters and GaN/AlN based quantum dots. We also show that one dimensional
ensembles substantially improve performances, even of CdSe/CdS based quantum
dots.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-265709.4235 | Extended matter coupled to BF theory
gr-qc
Recently, a topological field theory of membrane-matter coupled to BF theory
in arbitrary spacetime dimensions was proposed [1]. In this paper, we discuss
various aspects of the four-dimensional theory. Firstly, we study classical
solutions leading to an interpretation of the theory in terms of strings
propagating on a flat spacetime. We also show that the general classical
solutions of the theory are in one-to-one correspondence with solutions of
Einstein's equations in the presence of distributional matter (cosmic strings).
Secondly, we quantize the theory and present, in particular, a prescription to
regularize the physical inner product of the canonical theory. We show how the
resulting transition amplitudes are dual to evaluations of Feynman diagrams
coupled to three-dimensional quantum gravity. Finally, we remove the regulator
by proving the topological invariance of the transition amplitudes.
| arxiv topic:gr-qc |
arxiv_dataset-266709.4335 | Localization of an impurity particle on a boson Mott insulator
background
cond-mat.other
We investigate the behavior of a single particle hopping on a three
dimensional cubic optical lattice in the presence of a Mott insulator of bosons
in the same lattice. We calculate the critical interaction strength between the
impurity and background bosons, beyond which there is bound state (polaron)
formation. We give exact results in the limit of a perfect Mott insulator,
where polaron formation is equivalent to impurity localization. We calculate
the effects of lattice anisotropy, higher impurity bands, and fluctuations of
the Mott insulator on the localization threshold. We argue that our results can
be checked experimentally by RF spectroscopy of impurity particles.
| arxiv topic:cond-mat.other |
arxiv_dataset-267709.4435 | Invariants of differential equations defined by vector fields
math-ph math.DG math.MP
We determine the most general group of equivalence transformations for a
family of differential equations defined by an arbitrary vector field on a
manifold. We also find all invariants and differential invariants for this
group up to the second order. A result on the characterization of classes of
these equations by the invariant functions is also given.
| arxiv topic:math-ph math.DG math.MP |
arxiv_dataset-268709.4535 | Prospects of a Search for a New Massless Neutral Gauge Boson at the ILC
hep-ph
Prospects to search for a new massless neutral gauge boson, the paraphoton,
in e+ e- collisions at center-of-mass energies of 0.5 and 1 TeV are studied.
The paraphoton naturally appears in models with abelian kinetic mixing. A
possible realistic model independent lowest order effective Lagrangian contains
magnetic interactions of the paraphoton with the Standard Model fermion fields.
These interactions are proportional to the fermion mass and grow with energy,
with however very weak paraphoton couplings to ordinary matter. At the ILC, a
potentially interesting process to search for the paraphoton is its radiation
off top quarks, so that the event topology to be searched for is a pair of
acoplanar top quark jets with missing energy. By combining many discriminating
features of signal and background events efficient paraphoton event selection
was achieved allowing to set limits for the top-paraphoton coupling. Arguments
in favor of the missing energy as the paraphoton with spin 1 are discussed.
| arxiv topic:hep-ph |
arxiv_dataset-269709.4635 | Color superconductivity in dense quark matter
hep-ph astro-ph cond-mat.supr-con nucl-th
Matter at high density and low temperature is expected to be a color
superconductor, which is a degenerate Fermi gas of quarks with a condensate of
Cooper pairs near the Fermi surface that induces color Meissner effects. At the
highest densities, where the QCD coupling is weak, rigorous calculations are
possible, and the ground state is a particularly symmetric state, the
color-flavor locked (CFL) phase. The CFL phase is a superfluid, an
electromagnetic insulator, and breaks chiral symmetry. The effective theory of
the low-energy excitations in the CFL phase is known and can be used, even at
more moderate densities, to describe its physical properties. At lower
densities the CFL phase may be disfavored by stresses that seek to separate the
Fermi surfaces of the different flavors, and comparison with the competing
alternative phases, which may break translation and/or rotation invariance, is
done using phenomenological models. We review the calculations that underlie
these results, and then discuss transport properties of several
color-superconducting phases and their consequences for signatures of color
superconductivity in neutron stars.
| arxiv topic:hep-ph astro-ph cond-mat.supr-con nucl-th |
arxiv_dataset-270710.0053 | High-sensitivity imaging with multi-mode twin beams
quant-ph
Twin entangled beams produced by single-pass parametric down-conversion (PDC)
offer the opportunity to detect weak amount of absorption with an improved
sensitivity with respect to standard techniques which make use of classical
light sources. We propose a differential measurement scheme which exploits the
spatial quantum correlation of type II PDC to image a weak amplitude object
with a sensitivity beyond the standard quantum limit imposed by shot-noise.
| arxiv topic:quant-ph |
arxiv_dataset-271710.0153 | Omega-powers and descriptive set theory
math.LO math.GN
We study the sets of the infinite sentences constructible with a dictionary
over a finite alphabet, from the viewpoint of descriptive set theory. Among
other things, this gives some true co-analytic sets. The case where the
dictionary is finite is studied and gives a natural example of a set at the
level omega of the Wadge hierarchy.
| arxiv topic:math.LO math.GN |
arxiv_dataset-272710.0253 | Crystal graphs for general linear Lie superalgebras and quasi-symmetric
functions
math.RT math.QA
We give a new representation theoretic interpretation of the ring of
quasi-symmetric functions. This is obtained by showing that the super analogue
of the Gessel's fundamental quasi-symmetric function can be realized as the
character of an irreducible crystal for the Lie superalgebra $\frak{gl}_{n|n}$
associated to its non-standard Borel subalgebra with a maximal number of odd
isotropic simple roots. We also present an algebraic characterization of these
super quasi-symmetric functions.
| arxiv topic:math.RT math.QA |
arxiv_dataset-273710.0353 | Trap-imbalanced fermion mixtures
cond-mat.supr-con cond-mat.other
We analyze the ground state phases of two-component ($\sigma \equiv \lbrace
\uparrow, \downarrow \rbrace$) population- and mass-balanced ($N_\uparrow =
N_\downarrow$ and $m_\uparrow = m_\downarrow$) but trap-imbalanced
($\omega_\uparrow \ne \omega_\downarrow$) fermion mixtures as a function of
interaction strength from the weak attraction Bardeen-Cooper-Schrieffer (BCS)
to the strong attraction Bose-Einstein condensation (BEC) limit. In the BCS
limit, we find that the unpolarized superfluid (UPS) fermions exist away from
the central core of the trapping potentials, and are surrounded by partially
polarized normal (P$\sigma$PN) fermions. As the interactions increase towards
unitarity, we find that the central P$\sigma$PN core first transitions to a
UPS, and then expands towards the edges until the entire mixture becomes a UPS
in the BEC limit.
| arxiv topic:cond-mat.supr-con cond-mat.other |
arxiv_dataset-274710.0453 | Higher-spin Gauge and Trace Anomalies in Two-dimensional Backgrounds
hep-th gr-qc
Two-dimensional quantum fields in electric and gravitational backgrounds can
be described by conformal field theories, and hence all the physical
(covariant) quantities can be written in terms of the corresponding holomorphic
quantities. In this paper, we first derive relations between covariant and
holomorphic forms of higher-spin currents in these backgrounds, and then, by
using these relations, obtain higher-spin generalizations of the trace and
gauge (or gravitational) anomalies up to spin 4. These results are applied to
derive higher-moments of Hawking fluxes in black holes in a separate paper
arXiv:0710.0456.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-275710.0553 | Zooming in on light relic neutralinos by direct detection and
measurements of galactic antimatter
hep-ph astro-ph hep-ex
The DAMA Collaboration has recently analyzed its data of the extensive WIMP
direct search (DAMA/NaI) which detected an annual modulation, by taking into
account the channelling effect which occurs when an ion traverses a detector
with a crystalline structure. Among possible implications, this Collaboration
has considered the case of a coherent WIMP-nucleus interaction and then derived
the form of the annual modulation region in the plane of the WIMP-nucleon cross
section versus the WIMP mass, using a specific modelling for the channelling
effect. In the present paper we first show that light neutralinos fit the
annual modulation region also when channelling is taken into account. To
discuss the connection with indirect signals consisting in galactic antimatter,
in our analysis we pick up a specific galactic model, the cored
isothermal-sphere. In this scheme we determine the sets of supersymmetric
models selected by the annual modulation regions and then prove that these sets
are compatible with the available data on galactic antiprotons. We comment on
implications when other galactic distribution functions are employed. Finally,
we show that future measurements on galactic antiprotons and antideuterons will
be able to shed further light on the populations of light neutralinos singled
out by the annual modulation data.
| arxiv topic:hep-ph astro-ph hep-ex |
arxiv_dataset-276710.0653 | Study of the critical point in lattice QCD at high temperature and
density
hep-lat
We propose a method to probe the nature of phase transitions in lattice QCD
at finite temperature and density, which is based on the investigation of an
effective potential as a function of the average plaquette. We analyze data
obtained in a simulation of two-flavor QCD using p4-improved staggered quarks
with bare quark mass $m/T = 0.4$, and find that a first order phase transition
line appears in the high density regime for $\mu_q/T \sim 2.5$. The effective
potential as a function of the quark number density is also studied. We
calculate the chemical potential as a function of the density from the
canonical partition function and discuss the existence of the first order phase
transition line.
| arxiv topic:hep-lat |
arxiv_dataset-277710.0753 | Modelling Bonds & Credit Default Swaps using a Structural Model with
Contagion
q-fin.PR math.PR
This paper develops a two-dimensional structural framework for valuing credit
default swaps and corporate bonds in the presence of default contagion.
Modelling the values of related firms as correlated geometric Brownian motions
with exponential default barriers, analytical formulae are obtained for both
credit default swap spreads and corporate bond yields. The credit dependence
structure is influenced by both a longer-term correlation structure as well as
by the possibility of default contagion. In this way, the model is able to
generate a diverse range of shapes for the term structure of credit spreads
using realistic values for input parameters.
| arxiv topic:q-fin.PR math.PR |
arxiv_dataset-278710.0853 | Search for supersymmetric charged Higgs bosons at the TeVatron
hep-ex
The data collected at the TeVatron RunIIa have been used to look for
supersymmetric charged Higgs boson and Left-Right suspersymmetric doubly
charged Higgs boson. No signal of such bosons has been found and this note
reports on the current analyses and their observed excluded domains in models
parameter space.
| arxiv topic:hep-ex |
arxiv_dataset-279710.0953 | The AGB stars of the intermediate-age LMC cluster NGC 1846 Variability
and age determination
astro-ph
Aims: To investigate variability and to model the pulsational behaviour of
AGB variables in the intermediate-age LMC cluster NGC 1846.
Methods: Our own photometric monitoring has been combined with data from the
MACHO archive to detect 22 variables among the cluster's AGB stars and to
derive pulsation periods. According to the global parameters of the cluster we
construct pulsation models taking into account the effect of the C/O ratio on
the atmospheric structure. In particular, we have used opacities appropriate
for both O-rich stars and carbon stars in the pulsation calculations.
Results: The observed P-L-diagram of NGC 1846 can be fitted using a mass of
the AGB stars of about 1.8 M$_{\sun}$. We show that the period of pulsation is
increased when an AGB star turns into a carbon star. Using the mass on the AGB
defined by the pulsational behaviour of our sample we derive a cluster age of
$1.4\times10^{9}$ years. This is the first time the age of a cluster has been
derived from the variability of its AGB stars. The carbon stars are shown to be
a mixture of fundamental and first overtone radial pulsators.
| arxiv topic:astro-ph |
arxiv_dataset-280710.1053 | Extensions for supersingular representations of $GL_2(Q_p)$
math.RT math.NT
Let $p>2$ be a prime number. Let $G:=GL_2(Q_p)$ and $\pi$, $\tau$ smooth
irreducible representations of $G$ on $\bar{F}_p$-vector spaces with a central
character. We show if $\pi$ is supersingular then $Ext^1_G(\tau,\pi)\neq 0$
implies $\tau\cong \pi$. This answers affirmatively for $p>2$ a question of
Colmez. We also determine $Ext^1_G(\tau,\pi)$, when $\pi$ is the Steinberg
representation. As a consequence of our results combined with those already in
the literature one knows $Ext^1_G(\tau,\pi)$ for all irreducible
representations of $G$.
| arxiv topic:math.RT math.NT |
arxiv_dataset-281710.1153 | Verification of Ptime Reducibility for system F Terms: Type Inference
in<br> Dual Light Affine Logic
cs.LO cs.CC
In a previous work Baillot and Terui introduced Dual light affine logic
(DLAL) as a variant of Light linear logic suitable for guaranteeing complexity
properties on lambda calculus terms: all typable terms can be evaluated in
polynomial time by beta reduction and all Ptime functions can be represented.
In the present work we address the problem of typing lambda-terms in
second-order DLAL. For that we give a procedure which, starting with a term
typed in system F, determines whether it is typable in DLAL and outputs a
concrete typing if there exists any. We show that our procedure can be run in
time polynomial in the size of the original Church typed system F term.
| arxiv topic:cs.LO cs.CC |
arxiv_dataset-282710.1253 | The forgetful map in rational K-theory
math.AG math.KT
Let G be a connected reductive algebraic group acting on a scheme X. Let R(G)
denote the representation ring of G, and let I be the ideal in R(G) of virtual
representations of rank 0. Let G(X) (resp. G(G,X)) denote the Grothendieck
group of coherent sheaves (resp. G-equivariant coherent sheaves) on X.
Merkurjev proved that if the fundamental group of G is torsion-free, then the
map of G(G,X)/IG(G,X) to G(X) is an isomorphism. Although this map need not be
an isomorphism if the fundamental group of G has torsion, we prove that without
the assumption on the fundamental group of G, this map is an isomorphism after
tensoring with the rational numbers.
| arxiv topic:math.AG math.KT |
arxiv_dataset-283710.1353 | Exact Numerical Study of Pair Formation with Imbalanced Fermion
Populations
cond-mat.str-el
We present an exact Quantum Monte Carlo study of the attractive 1-dimensional
Hubbard model with imbalanced fermion population. The pair-pair correlation
function, which decays monotonically in the absence of polarization P, develops
oscillations when P is nonzero, characteristic of
Fulde-Ferrell-Larkin-Ovchinnikov phase. The pair momentum distribution peaks at
a momentum equal to the difference in the Fermi momenta. At strong coupling,
the minority and majority momentum distributions are shown to be deformed,
reflecting the presence of the other species, and its Fermi surface. The FFLO
oscillations survive the presence of a confining potential, and the local
polarization at the trap center exhibits a marked dip, similar to that observed
experimentally.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-284710.1453 | Hadron production in deuteron-gold collisions and nuclear parton
distributions
hep-ph
We calculate nuclear modification factors $R_{dAu}$, central-to-peripheral
ratios, $R_{CP}$, and pseudorapidity asymmetries $Y_{Asym}$ in deuteron-gold
collisions at $\sqrt{s} = 200$ GeV in the framework of leading-order (LO)
perturbative Quantum Chromodynamics. We use the Eskola-Kolhinen-Salgado (EKS),
the Frankfurt-Guzey-Strikman (FGS) and the Hirai-Kumano-Nagai (HKN) nuclear
parton distribution functions and the Albino-Kramer-Kniehl (AKK) fragmentation
functions in our calculations. Results are compared to experimental data from
the BRAHMS and STAR collaborations.
| arxiv topic:hep-ph |
arxiv_dataset-285710.1553 | Heavy-light decay constant at the 1/m order of HQET
hep-lat
Following the strategy developed by the ALPHA collaboration, we present a
method to compute non-perturbatively the decay constant of a heavy-light meson
in HQET including the 1/m corrections. We start by a matching between HQET and
QCD in a small volume to determine the parameters of the effective theory
non-perturbatively. Observables in the effective theory are then evolved to
larger volumes. In two steps a large enough volume is reached to determine the
physical decay constant. Some preliminary results in the quenched approximation
are shown.
| arxiv topic:hep-lat |
arxiv_dataset-286710.1653 | Superhumps and flickering in V1316 Cygni
astro-ph
We present analysis and results of a coordinated CCD photometry campaign to
observe the 2006 June superoutburst of the cataclysmic variable V1316 Cyg
involving 8 longitudinally-distributed observers. The outburst peaked at
magnitude 15.03 on June 10, declined at a rate of 0.14 mag/day, lasted 11 days
and had an amplitude above quiescence of 2.4 magnitudes. We detected common
superhumps for the first time, thereby confirming that V1316 Cyg is a member of
the UGSU class of dwarf novae. We observed a transition to late superhumps
two-thirds of the way through the outburst with an associated phase shift of
0.50 +/- 0.06 cycles. The mean common superhump period before this transition
was 0.07685 +/- 0.00003 d and the mean late superhump period following the
transition was 0.07654 +/- 0.00002 d. The common superhump period decreased at
a rate dP/dt = -5.1 +/- 1.7 x10^-5 /cycle. At the onset of late superhumps,
there was a transient shift in power from the superhump fundamental frequency
to its first harmonic and back again. We detected an orbital period of 0.0740
+/- 0.0002 d giving a fractional superhump period excess of 0.038 +/- 0.003 and
a mass ratio of 0.167 +/- 0.010. A scalegram analysis of the flickering
behaviour of V1316 Cyg found that the alpha and sigma parameters characterising
flickering changed significantly during the superoutburst. We also found
flickering to be at a relatively much lower level at the beginning of the
superoutburst and during two normal outbursts.
| arxiv topic:astro-ph |
arxiv_dataset-287710.1753 | A generalisation of the Cauchy-Kovalevskaia theorem
math.FA
I prove, under mild assumptions, that solutions to linear evolution equations
admit sectorial solutions. The size of the sector depends on the regularity of
the initial data. If it is regular enough the solution is holomorphic and
unique otherwise it is sectorial. I also prove that the result is optimal for
many partial differential systems (which includes KdV and other examples).
| arxiv topic:math.FA |
arxiv_dataset-288710.1853 | Engineering many-body quantum dynamics by disorder
cond-mat.dis-nn cond-mat.stat-mech
Going beyond the currently investigated regimes in experiments on quantum
transport of ultracold atoms in disordered potentials, we predict a crossover
between regular and quantum-chaotic dynamics when varying the strength of
disorder. Our spectral approach is based on the Bose-Hubbard model describing
interacting atoms in deep random potentials. The predicted crossover from
localized to diffusive dynamics depends on the simultaneous presence of
interactions and disorder, and can be verified in the laboratory by monitoring
the evolution of typical experimental initial states.
| arxiv topic:cond-mat.dis-nn cond-mat.stat-mech |
arxiv_dataset-289710.1953 | Strong Reduction of the Field-Dependent Microwave Surface Resistance in
YBCO with BaZrO_3 Inclusions
cond-mat.supr-con cond-mat.mtrl-sci
We present measurements of the magnetic field dependent microwave surface
resistance in laser-ablated YBa$_2$Cu$_3$O$_{7-\delta}$ films on SrTiO$_3$
substrates. BaZrO$_3$ crystallites were included in the films using composite
targets containing BaZrO$_3$ inclusions with mean grain size smaller than 1
$\mu$m. X-ray diffraction showed single epitaxial relationship between
BaZrO$_3$ and YBa$_2$Cu$_3$O$_{7-\delta}$. The effective surface resistance was
measured at 47.7 GHz for 60$< T <$90 K and 0$< \mu_0H <$0.8 T. The magnetic
field had a very different effect on pristine YBa$_2$Cu$_3$O$_{7-\delta}$ and
YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$, while for $\mu_0H=$0 only a reduction of
$T_c$ in the YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$ film was observed,
consistent with dc measurements. At low enough $T$, in moderate fields
YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$ exhibited an intrinsic thin film
resistance lower than the pure film. The results clearly indicate that
BaZrO$_3$ inclusions determine a strong reduction of the field-dependent
surface resistance. From the analysis of the data in the framework of simple
models for the microwave surface impedance in the mixed state we argue that
BaZrO$_3$ inclusions determine very steep pinning potentials.
| arxiv topic:cond-mat.supr-con cond-mat.mtrl-sci |
arxiv_dataset-290710.2053 | Fokker-Planck Equation for Fractional Systems
cond-mat.stat-mech
The normalization condition, average values and reduced distribution
functions can be generalized by fractional integrals. The interpretation of the
fractional analog of phase space as a space with noninteger dimension is
discussed. A fractional (power) system is described by the fractional powers of
coordinates and momenta. These systems can be considered as non-Hamiltonian
systems in the usual phase space. The generalizations of the Bogoliubov
equations are derived from the Liouville equation for fractional (power)
systems. Using these equations, the corresponding Fokker-Planck equation is
obtained.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-291710.2153 | Phase Separation and Charge Transfer in a K-doped C60 Monolayer on
Ag(001)
cond-mat.mtrl-sci
We have performed a scanning tunneling microscopy and spectroscopy study of
potassium-doped C60 monolayers (KxC60) on Ag(001) in the regime of x ~ 1. Low
temperature annealing (640 K) leads to the formation of two well-ordered KxC60
phases that exhibit differing levels of electron charge transfer. Further
annealing (710 K) distills out the higher electron-doped phase from the lower
electron-doped phase, leaving behind a third C60 phase completely devoid of K.
Spectroscopic measurements indicate that the electron-doping level of the
higher electron-doped KC60 phase is anomalously large.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-292710.2253 | McKay's correspondence for cocompact discrete subgroups of SU(1,1)
math.AG math.GT
The classical McKay correspondence establishes an explicit link from the
representation theory of a finite subgroup G of SU(2) and the geometry of the
minimal resolution of the quotient of the affine plane by G. In this paper we
discuss a possible generalization of the McKay correspondence to the case when
G is replaced with a cocompact discrete subgroup of the universal cover of
SU(1,1) such that its image in PSU(1,1) is a cocompact fuchsian group with
quotient of genus 0. We establish a correspondence between a certain class of
finite-dimensional unitary representations of G and vector bundles on an open
algebraic surface with the trivial canonical class canonically associated to G.
| arxiv topic:math.AG math.GT |
arxiv_dataset-293710.2353 | A Criterion For Ergodicity of Non-uniformly hyperbolic Diffeomorphisms
math.DS
In this work we exhibit a new criteria for ergodicity of diffeomorphisms
involving conditions on Lyapunov exponents and general position of some
invariant manifolds. On one hand we derive uniqueness of SRB-measures for
transitive surface diffeomorphisms. On the other hand, using recent results on
the existence of blenders we give a positive answer, in the $C^1$ topology, to
a conjecture of Pugh-Shub in the context of partially hyperbolic conservative
diffeomorphisms with two dimensional center bundle.
| arxiv topic:math.DS |
arxiv_dataset-294710.2453 | Quasi-Hermitian supersymmetric extensions of a non-Hermitian oscillator
Hamiltonian and of its generalizations
math-ph hep-th math.MP quant-ph
A harmonic oscillator Hamiltonian augmented by a non-Hermitian \pt-symmetric
part and its su(1,1) generalizations, for which a family of positive-definite
metric operators was recently constructed, are re-examined in a supersymmetric
context. Quasi-Hermitian supersymmetric extensions of such Hamiltonians are
proposed by enlarging su(1,1) to a ${\rm su}(1,1/1) \sim {\rm osp}(2/2, \R)$
superalgebra. This allows the construction of new non-Hermitian Hamiltonians
related by similarity to Hermitian ones. Some examples of them are reviewed.
| arxiv topic:math-ph hep-th math.MP quant-ph |
arxiv_dataset-295710.2553 | Capacity of Linear Two-hop Mesh Networks with Rate Splitting,
Decode-and-forward Relaying and Cooperation
cs.IT math.IT
A linear mesh network is considered in which a single user per cell
communicates to a local base station via a dedicated relay (two-hop
communication). Exploiting the possibly relevant inter-cell channel gains, rate
splitting with successive cancellation in both hops is investigated as a
promising solution to improve the rate of basic single-rate communications.
Then, an alternative solution is proposed that attempts to improve the
performance of the second hop (from the relays to base stations) by cooperative
transmission among the relay stations. The cooperative scheme leverages the
common information obtained by the relays as a by-product of the use of rate
splitting in the first hop. Numerical results bring insight into the conditions
(network topology and power constraints) under which rate splitting, with
possible relay cooperation, is beneficial. Multi-cell processing (joint
decoding at the base stations) is also considered for reference.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-296710.2653 | A Supersymmetric U(1)' Model with Multiple Dark Matters
hep-ph
We consider a scenario where a supersymmetric model has multiple dark matter
particles. Adding a U(1)' gauge symmetry is a well-motivated extension of the
Minimal Supersymmetric Standard Model (MSSM). It can cure the problems of the
MSSM such as the mu-problem or the proton decay problem with high-dimensional
lepton number and baryon number violating operators which R-parity allows. An
extra parity (U-parity) may arise as a residual discrete symmetry after U(1)'
gauge symmetry is spontaneously broken. The Lightest U-parity Particle (LUP) is
stable under the new parity becoming a new dark matter candidate. Up to three
massive particles can be stable in the presence of the R-parity and the
U-parity. We numerically illustrate that multiple stable particles in our model
can satisfy both constraints from the relic density and the direct detection,
thus providing a specific scenario where a supersymmetric model has
well-motivated multiple dark matters consistent with experimental constraints.
The scenario provides new possibilities in the present and upcoming dark matter
searches in the direct detection and collider experiments.
| arxiv topic:hep-ph |
arxiv_dataset-297710.2753 | Effects of anharmonic vibration on large-angle quasi-elastic scattering
of 16O+144Sm
nucl-th
We study the effects of double octupole and quadrupole phonon excitations in
the 144Sm nucleus on quasi-elastic 16O+144Sm scattering at backward angles. To
this end, we use the coupled-channels framework, taking into account explicitly
the anharmonicities of the vibrations. We use the same coupling scheme as that
previously employed to explain the experimental data of sub-barrier fusion
cross sections for the same system. We show that the experimental data for the
quasi-elastic cross sections are well reproduced in this way, although the
quasi-elastic barrier distribution has a distinct high energy peak which is
somewhat smeared in the experimental barrier distribution. We also discuss the
effects of proton transfer on the quasi-elastic barrier distribution. Our study
indicates that the fusion and quasi-elastic barrier distributions for this
system cannot be accounted for simultaneously with the standard
coupled-channels approach.
| arxiv topic:nucl-th |
arxiv_dataset-298710.2853 | Exotic hadrons and SU(3) chiral dynamics
hep-ph nucl-th
We explore a possibility to generate exotic hadrons dynamically in the
scattering of hadrons. The s-wave scattering amplitude of an arbitrary hadron
with the Nambu-Goldstone boson is constructed so as to satisfy the unitarity
condition and the chiral low energy theorem. We find that the chiral
interaction for the exotic channels is in most cases repulsive, and that the
strength of the possible attractive interaction is uniquely determined. We show
that the attractive interaction in exotic channels is not strong enough to
generate a bound state, while the interaction in nonexotic channel generate
bound states which are considered to be the origin of some resonances observed
in nature.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-299710.2953 | A Quantum Singlet Pump
cond-mat.mes-hall
We provide provide a detailed study of biasless coherent transport of singlet
electron pairs in one-dimensional (1D) channels induced by electron-electron
interactions that are time-varying in certain spatially localized regions of
the channel. When the time variation is cyclic, the mechanism is analogous to
the adiabatic quantum pumping of charge and spin previously studied. However,
the presence of interactions that vary only in localized regions of space
requires an intrinsically two-body description which is irreducible to the 1D
single particle scattering matrix elements that are sufficient to describe
quantum pumping of charge and spin. Here we derive a generalized theory for the
pumping of such interacting pairs starting from first principles. We show that
the standard description of charge pumping is contained within our more broadly
applicable expressions. We then apply our general results to a concrete lattice
model and obtain an exact analytical expression for the pumped singlet current.
We further demonstrate that such a model can be implemented with a chain of
currently available quantum dots with certain minor modifications that we
suggest; we present a detailed numerical feasibility analysis of the
characteristics of such experimentally realizable quantum dots, showing that
the requirements for a measurable pumped singlet current are within
experimental range.
| arxiv topic:cond-mat.mes-hall |
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