publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2006-02-06 | Thermoelectric effects in a strongly interacting quantum dot coupled to ferromagnetic leads | We study thermoelectric effects in Kondo correlated quantum dot coupled to
ferromagnetic electrodes by calculating thermopower S in the Kondo regime as
function of on-dot energy level and temperature. The system is represented by
the Anderson model and the results agree well with those recently measured for
a quantum d... | 0602121v1 |
2006-02-08 | Strong coupling theory for the superfluidity of Bose-Fermi mixtures | We develop a strong-coupling theory for the superfluidity of fermion pairing
phase in a Bose-Fermi mixture. Dynamical screening, self-energy
renormalization, and a pairing gap function are included self-consistently
within the adiabatic limit (i.e., the phonon velocity is much smaller than the
Fermi velocity). An analy... | 0602201v2 |
2006-03-14 | Molecular states in carbon nanotube double quantum dots | We report electrical transport measurements through a semiconducting
single-walled carbon nanotube (SWNT) with three additional top-gates. At low
temperatures the system acts as a double quantum dot with large inter-dot
tunnel coupling allowing for the observation of tunnel-coupled molecular states
extending over the w... | 0603367v1 |
2006-03-20 | Influence of lattice distortions in classical spin systems | We investigate a simple model of a frustrated classical spin chain coupled to
adiabatic phonons under an external magnetic field. A thorough study of the
magnetization properties is carried out both numerically and analytically. We
show that already a moderate coupling with the lattice can stabilize a plateau
at 1/3 of... | 0603514v2 |
2006-04-12 | On the generation of multipartite entangled states in Josephson architectures | We propose and analyze a scheme for the generation of multipartite entangled
states in a system of inductively coupled Josephson flux qubits. The qubits
have fixed eigenfrequencies during the whole process in order to minimize
decoherence effects and their inductive coupling can be turned on and off at
will by tuning a... | 0604313v1 |
2006-04-21 | Dissipationless spin-current between Heisenberg ferromagnets with spin-orbit coupling | A system exhibiting multiple simultaneously broken symmetries offers the
opportunity to influence physical phenomena such as tunneling currents by means
of external control parameters. Time-reversal symmetry and inversion symmetry
are both absent in ferromagnetic metals with substantial spin-orbit coupling.
We here stu... | 0604510v1 |
2006-05-05 | Cavity quantum electrodynamics with semiconductor double-dot molecules on a chip | We describe a coherent control technique for coupling electron spin states
associated with semiconductor double-dot molecule to a microwave stripline
resonator on a chip. We identify a novel regime of operation in which strong
interaction between a molecule and a resonator can be achieved with minimal
decoherence, reac... | 0605144v1 |
2006-05-13 | Scattering wave function approach to multi-terminal mesoscopic system with spin-orbit coupling | In this paper,we present a detailed formulation to solve the scattering wave
function for a multi-terminal mesoscopic system with spin-orbit coupling. In
addition to terminal currents, all local quantities can be calculated
explicitly by taking proper ensemble average in the Landauer-Buttiker's spirit
using the scatter... | 0605361v1 |
2006-06-16 | Electronic states of laterally coupled quantum rings | The conduction band electron states of laterally-coupled semiconductor
quantum rings are studied within the frame of the effective mass envelope
function theory. We consider the effect of axial and in-plane magnetic fields
for several inter-ring distances, and find strong changes in the energy
spectrum depending on the... | 0606438v1 |
2006-06-29 | Relevance of quantum fluctuations in the Anderson-Kondo model | We study a localized spin coupled to an Anderson impurity to model the
situation found in higher transition metal or rare earth compounds like e.g.\
LaMnO$_3$ or Gd monopnictides. We find that, even for large quantum numbers of
the localized spin, quantum fluctuations play an essential role for the case of
ferromagneti... | 0606762v1 |
2006-07-07 | Phase diagram of the spin-Peierls chain with local coupling | We explore the ground-state phase diagram of a Heisenberg spin chain coupled
locally to optical phonons (bond coupling), using large-scale density matrix
renormalization group calculations and an extended perturbative analysis. For
the quantum phase transition from the spin liquid to the dimerized phase, we
find deviat... | 0607209v1 |
2006-07-08 | Harper-Hofstadter problem for 2D electron gas with ${\bf k}$-linear Rashba spin-orbit coupling | The Harper-Hofstadter problem for two-dimensional electron gas with Rashba
spin-orbit coupling subject to periodic potential and perpendicular magnetic
field is studied analytically and numerically. The butterfly-like energy
spectrum, spinor wave functions as well as the spin density and average spin
polarization are c... | 0607216v1 |
2006-07-25 | Quantum Hall Ferrimagnetism in lateral quantum dot molecules | We demonstrate the existance of ferrimagnetic and ferromagnetic phases in a
spin phase diagram of coupled lateral quantum dot molecules in the quantum Hall
regime. The spin phase diagram is determined from Hartree-Fock Configuration
Interaction method as a function of electron numbers N, magnetic field B,
Zeeman energy... | 0607638v1 |
2006-07-27 | Time-dependent evolution of two coupled Luttinger liquids | We consider two disconnected Luttinger liquids which are coupled at $t=0$
through chiral density-density interactions. Both for $t<0$ and $t \geq 0$ the
system is exactly solvable by means of bosonization and this allows to evaluate
analytically the time-dependence of correlation functions. We find that in the
long-tim... | 0607720v2 |
2006-07-28 | Kondo effect in coupled quantum dots with RKKY interaction: Finite temperature and magnetic field effects | We study transport through two quantum dots coupled by an RKKY interaction as
a function of temperature and magnetic field. By applying the Numerical
Renormalization Group (NRG) method we obtain the transmission and the linear
conductance. At zero temperature and magnetic field, we observe a quantum phase
transition be... | 0607772v1 |
2006-08-07 | Quantum dynamics of a resonator driven by a superconducting single-electron transistor: a solid-state analogue of the micromaser | We investigate the behavior of a quantum resonator coupled to a
superconducting single-electron transistor tuned to the Josephson quasiparticle
resonance and show that the dynamics is similar in many ways to that found in a
micromaser. Coupling to the SSET can drive the resonator into non-classical
states of self-susta... | 0608166v2 |
2006-08-29 | Sequential Tunneling through Molecular Spin Rings | We consider electrical transport through molecules with Heisenberg-coupled
spins arranged in a ring structure in the presence of an easy-axis anisotropy.
The molecules are coupled to two metallic leads and a gate. In the charged
state of the ring, a Zener double-exchange mechanism links transport properties
to the unde... | 0608642v2 |
2006-09-19 | Far Infrared absorption of non center of mass modes and optical sum rule in a few electron quantum dot with Rashba spin-orbit coupling | Spin-orbit interaction in a quantum dot couples far infrared radiation to non
center of mass excitation modes, even for parabolic confinement and dipole
approximation. The intensities of the absorption peaks satisfy the optical sum
rule, giving direct information on the total number of electrons inside the
dot. In the ... | 0609456v1 |
2006-09-22 | Influence of thermal coupling on spin avalanches in Mn12-acetate | The effect of thermal coupling on spin avalanches in Mn12-acetate has been
probed using a single crystal assembly. Time-resolved, synchronized
measurements of magnetization and temperature are reported. Unusually low
avalanche trigger fields occur when thermal coupling to the bath is weak. A
temperature rise observed a... | 0609586v2 |
2006-10-04 | Correlated electrons systems on the Apollonian network | Strongly correlated electrons on an Apollonian network are studied using the
Hubbard model. Ground-state and thermodynamic properties, including specific
heat, magnetic susceptibility, spin-spin correlation function, double occupancy
and one-electron transfer, are evaluated applying direct diagonalization and
quantum M... | 0610111v1 |
2006-10-04 | Calculation of overdamped c-axis charge dynamics and the coupling to polar phonons in cuprate superconductors | In our recent paper we presented empirical evidences suggesting that
electrons in cuprate superconductors are strongly coupled to unscreened c-axis
polar phonons. In the overdoped regime the c-axis metallizes and we present
here simple theoretical arguments demonstrating that the observed effect of the
metallic c-axis ... | 0610129v1 |
2006-10-11 | Conductance of a molecule with a center of mass motion | We calculate the zero temperature conductance and characteristic correlation
functions of a molecule with a center of mass (CM) motion which modulates
couplings to the leads. In the first model studied, the CM vibrational mode is
simultaneously coupled to the electron density on the molecule. The conductance
is suppres... | 0610296v1 |
2006-10-25 | Interlayer exchange coupling in (Ga,Mn)As based multilayers | Exhibiting antiferromagnetic interlayer coupling in dilute magnetic
semiconductor multilayers is essential for the realisation of
magnetoresistances analogous to giant magnetoresistance in metallic multilayer
structures. In this work we use a mean-field theory of carrier induced
ferromagnetism to explore possible (Ga,M... | 0610696v1 |
2006-12-12 | Spin-orbit induced spin-qubit control in nanowires | We elaborate on a number of issues concerning our recent proposal for
spin-qubit manipulation in nanowires using the spin-orbit coupling. We discuss
the experimental status and describe in further detail the scheme for
single-qubit rotations. We present a derivation of the effective two-qubit
coupling which can be exte... | 0612293v1 |
2006-12-19 | Excitonic gap, phase transition, and quantum Hall effect in graphene: strong-coupling regime | We suggest that physics underlying the recently observed removal of
sublattice and spin degeneracies in graphene in a strong magnetic field
describes a phase transition connected with the generation of excitonic and
spin gaps. The strong-coupling regime is described using a phenomenological
model with enhanced Zeeman s... | 0612488v1 |
2006-12-21 | Spin wave excitations: The main source of the temperature dependence of Interlayer exchange coupling in nanostructures | Quantum mechanical calculations based on an extended Heisenberg model are
compared with ferromagnetic resonance (FMR) experiments on prototype trilayer
systems Ni_7/Cu_n/Co_2/Cu(001) in order to determine and separate for the first
time quantitatively the sources of the temperature dependence of interlayer
exchange cou... | 0612568v1 |
2007-01-06 | Spin Ladder with Anisotropic Ferromagnetic Legs in a Transverse Magnetic Field | We study the ground state phase diagram of a two-leg spin ladder with
anisotropic ferromagnetic leg couplings under the influence of a symmetry
breaking transverse magnetic field by the exact diagonalization technique. In
the case of antiferromagnetic coupling between legs we identified two phase
transitions in the pla... | 0701127v1 |
2007-01-15 | Non-local effective medium of metamaterial | In this paper, we investigate the effect of spatial dispersion on a
double-lattice metamaterial which has both magnetic and electric response. A
numerical scheme based on a dipolar model is developed to extract the non-local
effective medium of the metamaterial. We found a structure-induced bianisotropy
near the resona... | 0701332v1 |
2007-01-18 | Cooperative Effect of Electron Correlation and Spin-Orbit Coupling on the Electronic and Magnetic Properties of Ba2NaOsO6 | The electronic and magnetic properties of the cubic double perovskite
Ba2NaOsO6 were examined by performing first-principles density functional
theory calculations and analyzing spin-orbit coupled states of an Os7+ (d1) ion
at an octahedral crystal field. The insulating behavior of Ba2NaOsO6 was shown
to originate from... | 0701460v1 |
2007-01-24 | Non-markovian dynamics of double quantum dot charge qubit with static bias | The dynamics of charge qubit in double quantum dot coupled to phonons is
investigated theoretically. The static bias is considered. By means of the
perturbation approach based on unitary transformations, the dynamical tunneling
current is obtained explicitly. The biased system displays broken symmetry and
a significant... | 0701581v1 |
2007-01-25 | Spin-polarization coupling in multiferroic transition-metal oxides | A systematic microscopic theory of magnetically induced ferroelectricity and
lattice modulation is presented for all electron configurations of
Mott-insulating transition-metal oxides. Various mechanisms of polarization are
identified in terms of a strong-coupling perturbation theory. Especially, the
spin-orbit interac... | 0701614v1 |
2007-01-26 | Entrainment transition in populations of random frequency oscillators | The entrainment transition of coupled random frequency oscillators is
revisited. The Kuramoto model (global coupling) is shown to exhibit unusual
sample-dependent finite size effects leading to a correlation size exponent
$\bar\nu=5/2$. Simulations of locally coupled oscillators in $d$-dimensions
reveal two types of fr... | 0701646v2 |
2007-02-28 | Non-collinear coupling between magnetic adatoms in carbon nanotubes | The long range character of the exchange coupling between localized magnetic
moments indirectly mediated by the conduction electrons of metallic hosts often
plays a significant role in determining the magnetic order of low-dimensional
structures. In addition to this indirect coupling, here we show that the direct
excha... | 0703007v1 |
2007-03-02 | Topological Force and Torque in Spin-Orbit Coupling System | The topological force and torque are investigated in the systems with
spin-orbit coupling. Our results show that the topological force and torque
appears as a pure relativistic quantum effect in an electromagnetic field. The
origin of both topological force and torque is the Zitterbewegung effect.
Considering nonlinear... | 0703048v1 |
2007-03-23 | Transport through a molecular quantum dot in the polaron crossover regime | We consider resonant transport through a molecular quantum dot coupled to a
local vibration mode. Applying the non-equilibrium Green function technique in
the polaron representation, we develop a non-perturbative scheme to calculate
the electron spectral function of the molecule in the regime of intermediate
electron-p... | 0703626v1 |
2005-08-26 | Long-term neuronal behavior caused by two synaptic modification mechanisms | We report the first results of simulating the coupling of neuronal,
astrocyte, and cerebrovascular activity. It is suggested that the dynamics of
the system is different from systems that only include neurons. In the
neuron-vascular coupling, distribution of synapse strengths affects neuronal
behavior and thus balance ... | 0508117v1 |
1992-07-20 | Non-Minimally Coupled Scalar Field and Ashtekar Variables | The non-minimal coupling of a scalar field is considered in the framework of
Ashtekar's new variables formulation of gravity. A first order action
functional for this system is derived in which the field variables are a tetrad
field, and an SL(2,C) connection, together with the scalar field. The tetrad
field and the SL... | 9207001v1 |
1993-02-10 | Cosmology with Nonminimal Derivative Couplings | We study a theory which generalizes the nonminimal coupling of matter to
gravity by including derivative couplings. This leads to several interesting
new dynamical phenomena in cosmology. In particular, the range of parameters in
which inflationary attractors exist is greatly expanded. We also numerically
integrate the... | 9302010v1 |
1994-06-30 | Preferred Basis in a Measurement Process | The effect of decoherence is analysed for a free particle, interacting with
an environment via a dissipative coupling. The interaction between the particle
and the environment occurs by a coupling of the position operator of the
particle with the environmental degrees of freedom. By examining the exact
solution of the ... | 9406054v1 |
1994-11-29 | String theory and gravity | It is pointed out that string-loop effects may generate matter couplings for
the dilaton allowing this scalar partner of the tensorial graviton to stay
massless while contributing to macroscopic gravity in a way naturally
compatible with existing experimental data. Under a certain assumption of
universality of the dila... | 9411069v1 |
1995-01-09 | Gravitational Constraints which Generate a Lie Algebra | The coupling of gravity to dust helps to discover simple quadratic
combinations of the gravitational super-Hamiltonian and supermomentum whose
Poisson brackets strongly vanish. This leads to a new form of vacuum
constraints which generate a true Lie algebra. We show that the coupling of
gravity to a massless scalar fie... | 9501005v1 |
1995-01-20 | Energy Density of Non-Minimally Coupled Scalar Field Cosmologies | Scalar fields coupled to gravity via $\xi R {\Phi}^2$ in arbitrary
Friedmann-Robertson-Walker backgrounds can be represented by an effective flat
space field theory. We derive an expression for the scalar energy density where
the effective scalar mass becomes an explicit function of $\xi$ and the scale
factor. The scal... | 9501022v1 |
1995-03-10 | A POSSIBLE SOLUTION TO THE PROBLEM OF EXTRA DIMENSIONS | We consider a multidimensional universe with the topology $M= \R\times
M_1\times \cdots \times M_n$, where the $M_i$ ($i>1$) are $d_i$-dimensional
Ricci flat spaces. Exploiting a conformal equivalence between minimal coupling
models and conformal coupling models, we get exact solutions for such an
universe filled by a ... | 9503018v1 |
1995-04-19 | Rotating Dilaton Black Holes | We consider the axially symmetric coupled system of gravitation,
electromagnetism and a dilaton field. Reducing from four to three dimensions,
the system is described by gravity coupled to a non-linear $\sigma$-model. We
find the target space isometries and use them to generate new solutions. It
seems that it is only p... | 9504027v1 |
1996-08-15 | Conformally coupled dark matter | Dark matter is obtained from a scalar field coupled conformally to
gravitation; the scalar being a relict of Dirac's gauge function. This
conformally coupled dark matter includes a gas of very light ($m\approx
2.25\times 10^{-34} eV$) neutral bosons having spin 0, as well as a
time-dependent global scalar field, both p... | 9608035v1 |
1997-08-21 | Torsion and the Electromagnetic Field | In the framework of the teleparallel equivalent of general relativity, we
study the dynamics of a gravitationally coupled electromagnetic field. It is
shown that the electromagnetic field is able not only to couple to torsion, but
also, through its energy-momentum tensor, to produce torsion. Furthermore, it
is shown th... | 9708051v2 |
1998-02-12 | Hamilton-Jacobi Solutions for Strongly-Coupled Gravity and Matter | A Green's function method is developed for solving strongly-coupled gravity
and matter in the semiclassical limit. In the strong-coupling limit, one
assumes that Newton's constant approaches infinity. As a result, one may
neglect second order spatial gradients, and each spatial point evolves like an
homogeneous univers... | 9802025v1 |
1998-06-29 | Self-Similar Collapse of Scalar Field in Higher Dimensions | This paper constructs continuously self-similar solution of a spherically
symmetric gravitational collapse of a scalar field in n dimensions. The
qualitative behavior of these solutions is explained, and closed-form answers
are provided where possible. Equivalence of scalar field couplings is used to
show a way to gene... | 9806112v2 |
1999-03-01 | Cosmological scaling solutions of non-minimally coupled scalar fields | We study the existence and stability of cosmological scaling solutions of a
non-minimally coupled scalar field evolving in either an exponential or inverse
power law potential. We show that for inverse power law potentials there exist
scaling solutions the stability of which does not depend on the coupling
constant $\x... | 9903004v1 |
1999-06-02 | Non-universal gravitational couplings of neutrinos in matter | When neutrinos travel through a normal matter medium, the electron neutrinos
couple differently to gravity compared to the other neutrinos, due to the
presence of electrons in the medium and the absence of the other charged
leptons. The matter-induced gravitational couplings of the neutrinos under such
conditions are c... | 9906006v1 |
1999-06-15 | Nonminimal Derivative Couplings and Inflation in Generalized Theories of Gravity | We study extended theories of gravity where nonminimal derivative couplings
of the form $R^{kl}\phi_{, k}\phi_{, l}$ are present in the Lagrangian. We show
how and why the other couplings of similar structure may be ruled out and then
deduce the field equations and the related cosmological models. Finally, we get
infla... | 9906051v1 |
1999-08-09 | Traversable wormholes from massless conformally coupled scalar fields | The massless conformally coupled scalar field is characterized by the
so-called "new improved stress-energy tensor", which is capable of classically
violating the null energy condition. When coupled to Einstein gravity we find a
three-parameter class of exact solutions. These exact solutions include the
Schwarzschild g... | 9908029v1 |
2000-02-01 | Nonminimal global monopoles and bound orbits | We perform a numerical analysis of the gravitational field of a global
monopole coupled nonminimally to gravity, and find that, for some given
nonminimal couplings (in constrast with the minimal coupling case), there is an
attractive region where bound orbits exist. We exhibit the behavior of the
frequency shifts that ... | 0002001v1 |
2000-02-26 | Inflation and quintessence with nonminimal coupling | The nonminimal coupling (NMC) of the scalar field to the Ricci curvature is
unavoidable in many cosmological scenarios. Inflation and quintessence models
based on nonminimally coupled scalar fields are studied, with particular
attention to the balance between the scalar potential and the NMC term in the
action. NMC mak... | 0002091v2 |
2000-03-13 | Double Scalar-Tensor Gravity Cosmologies | We investigate homogeneous and isotropic cosmological models in scalar-tensor
theories of gravity where two scalar fields are nonminimally coupled to the
geometry. Exact solutions are found, by Noether symmetries, depending on the
form of couplings and self-interaction potentials. An interesting feature is
that we deal... | 0003048v1 |
2000-04-03 | Generalized slow-roll inflation | The slow-roll approximation to inflation is ultimately justified by the
presence of inflationary attractors for the orbits of the solutions of the
dynamical equations in phase space. There are many indications that the
inflaton field couples nonminimally to the spacetime curvature: the existence
of attractor points for... | 0004007v2 |
2000-09-28 | Dilaton Gravity with a Non-minmally Coupled Scalar Field | We discuss the two-dimensional dilaton gravity with a scalar field as the
source matter. The coupling between the gravity and the scalar, massless, field
is presented in an unusual form. We work out two examples of these couplings
and solutions with black-hole behaviour are discussed and compared with those
found in th... | 0009097v1 |
2001-04-30 | Teleparallel Spin Connection | A new expression for the spin connection of teleparallel gravity is proposed,
given by minus the contorsion tensor plus a zero connection. The corresponding
minimal coupling is covariant under local Lorentz transformation, and
equivalent to the minimal coupling prescription of general relativity. With
this coupling pre... | 0104102v1 |
2002-01-05 | Exact Foldy-Wouthuysen transformation for spin 0 particle in curved space | Up to now, the only known exact Foldy- Wouthuysen transformation (FWT) in
curved space is that concerning Dirac particles coupled to static spacetime
metrics. Here we construct the exact FWT related to a real spin-0 particle for
the aforementioned spacetimes. This exact transformation exists independently
of the value ... | 0201015v3 |
2002-01-14 | On the existence of self-similar spherically symmetric wave maps coupled to gravity | We present a detailed analytical study of spherically symmetric self-similar
solutions in the SU(2) sigma model coupled to gravity. Using a shooting
argument we prove that there is a countable family of solutions which are
analytic inside the past self-similarity horizon. In addition, we show that for
sufficiently smal... | 0201046v1 |
2002-01-22 | On Consistence of Material Coupling in a GL(3,R) Gauge Formulation of Gravity | A covariant scheme for material coupling with $GL(N,R)$ gauge formulation of
gravity is studied. We revisit a known idea of a Yang-Mills type construction,
where quadratical power of cosmological constant have to be considered in
consistence with vacuum Einstein's gravity. Then, matter coupling with gravity
is introduc... | 0201072v3 |
2002-05-06 | On the stability of gravity in the presence of a non-minimally coupled scalar field | We show that Einstein's gravity coupled to a non-minimally coupled scalar
field is stable even for high values of the scalar field, when the sign of the
Einstein-Hilbert action is reversed. We also discuss inflationary solutions and
a possible new mechanism of reheating. | 0205022v2 |
2002-09-21 | Gravitating Isovector Solitons | We formulate the nonlinear isovector model in a curved background, and
calculate the spherically symmetric solutions for weak and strong coupling
regimes. The usual belief that gravity does not have appreciable effects on the
structure of solitons will be examined, in the framework of the calculated
solutions, by compa... | 0209074v1 |
2002-10-16 | Spin Foam Models of Yang-Mills Theory Coupled to Gravity | We construct a spin foam model of Yang-Mills theory coupled to gravity by
using a discretized path integral of the BF theory with polynomial interactions
and the Barret-Crane ansatz. In the Euclidian gravity case we obtain a vertex
amplitude which is determined by a vertex operator acting on a simple spin
network funct... | 0210051v1 |
2002-11-13 | On Consistence of Matter Coupling in GL(3,R) Gauge Formulation of Gravity | A covariant scheme for matter coupling with a GL(3,R) gauge formulation of
gravity is studied. We revisit a known Yang-Mills type construction, where
quadratical power of cosmological constant have to be considered in consistence
with vacuum Einstein's gravity. Then, matter coupling with gravity is
introduced and some ... | 0211048v1 |
2002-12-11 | "No-Scalar-Hair" Theorems for Nonminimally Coupled Fields with Quartic Self-Interaction | Self-gravitating scalar fields with nonminimal coupling to gravity and having
a quartic self-interaction are considered in the domain of outer communications
of a static black hole. It is shown that there is no value of the nonminimal
coupling parameter $\zeta$ for which nontrivial static black hole solutions
exist. Th... | 0212050v1 |
2003-03-26 | Collision of Electromagnetic Shock Waves Coupled with Axion Waves: An Example | We present an exact solution that describes collision of electromagnetic
shock waves coupled with axion plane waves. The axion has a rather special
coupling to the cross polarization term of the metric. The initial data on the
null surfaces is well-defined and collision results in a singularity free
interaction region.... | 0303102v1 |
2003-05-02 | A note on dualities in Einstein's gravity in the presence of a non-minimally coupled scalar field | We show that the action of Einstein's gravity with a scalar field coupled in
a generic way to spacetime curvature is invariant under a particular set of
conformal transformations. These transformations relate dual theories for which
the effective couplings of the theory are scaled uniformly. In the simplest
case, this ... | 0305009v1 |
2003-06-05 | Pioneer Anomaly and the Helicity-Rotation Coupling | The modification of the Doppler effect due to the coupling of the helicity of
the radiation with the rotation of the source/receiver is considered in the
case of the Pioneer 10/11 spacecraft. We explain why the Pioneer anomaly is not
influenced by the helicity-rotation coupling. | 0306024v2 |
2003-12-21 | Some Remarks on the Coupling Prescription of Teleparallel Gravity | By using a nonholonomic moving frame version of the general covariance
principle, an active version of the equivalence principle, an analysis of the
gravitational coupling prescription of teleparallel gravity is made. It is
shown that the coupling prescription determined by this principle is always
equivalent with the ... | 0312093v2 |
2003-12-29 | The interaction between graviton spin and gravitomagnetic fields | This note is devoted to the detailed mathematical treatment of the coupling
of graviton spin to gravitomagnetic fields. The expression (i.e., $\sim
g_{0m}\dot{g}_{0n}(\partial_{m}g_{0n}-\partial_{n}g_{0m})$) for the graviton
spin-gravitomagnetic (S-G) coupling in the Lagrangian/Hamiltonian density of
the weak gravitati... | 0312116v3 |
2004-02-16 | QED Coupling from a 5-D Kaluza-Klein Theory | We discuss the possibility to obtain, from a five-dimensional free spinor
Lagrangian, the Quantum Electro-Dynamics (QED) coupling via a Kaluza-Klein
reduction of the theory. This result is achieved taking a phase dependence of
the spinor field on the extra-coordinate and modifying the corresponding
connection. The five... | 0402073v1 |
2004-04-13 | Unruh response functions for scalar fields in de Sitter space | We calculate the response functions of a freely falling Unruh detector in de
Sitter space coupled to scalar fields of different coupling to the curvature,
including the minimally coupled massless case. Although the responses differ
strongly in the infrared as a consequence of the amplification of superhorizon
modes, th... | 0404058v2 |
2004-06-14 | Spin, Acceleration and Gravity | The massless field perturbations of the accelerating Minkowski and
Schwarzschild spacetimes are studied. The results are extended to the
propagation of the Proca field in Rindler spacetime. We examine critically the
possibility of existence of a general spin-acceleration coupling in complete
analogy with the well-known... | 0406061v1 |
2005-02-14 | Metric Redefinitions in Einstein-Aether Theory | `Einstein-Aether' theory, in which gravity couples to a dynamical, time-like,
unit-norm vector field, provides a means for studying Lorentz violation in a
generally covariant setting. Demonstrated here is the effect of a redefinition
of the metric and vector field in terms of the original fields and two free
parameters... | 0502066v2 |
2005-03-05 | Hamiltonian analysis of $n$-dimensional Palatini gravity with matter | We consider the Palatini formalism of gravity with cosmological constant
$\Lambda$ coupled to a scalar field $\phi$ in $n$-dimensions. The
$n$-dimensional Einstein equations with $\Lambda$ can be derived by the
variation of the coupled Palatini action provided $n>2$. The Hamiltonian
analysis of the coupled action is ca... | 0503024v1 |
2005-03-30 | The String Coupling Accelerates the Expansion of the Universe | Generic cosmological models in non-critical string theory have a
time-dependent dilaton background at a late epoch. The cosmological
deceleration parameter Q_0 is given by the square of the string coupling,
g_s^2, up to a negative sign. Hence the expansion of the Universe must
accelerate eventually, and the observed va... | 0503120v1 |
2005-06-10 | A group field theory for 3d quantum gravity coupled to a scalar field | We present a new group field theory model, generalising the Boulatov model,
which incorporates both 3-dimensional gravity and matter coupled to gravity. We
show that the Feynman diagram amplitudes of this model are given by Riemannian
quantum gravity spin foam amplitudes coupled to a scalar matter field. We
briefly dis... | 0506067v2 |
2005-08-29 | Spacetime symmetries and varying scalars | This talk discusses the relation between spacetime-dependent scalars, such as
couplings or fields, and the violation of Lorentz symmetry. A specific
cosmological supergravity model demonstrates how scalar fields can acquire
time-dependent expectation values. Within this cosmological background,
excitations of these sca... | 0508122v1 |
2005-09-28 | Massless DKP field in Lyra manifold | Massless scalar and vector fields are coupled to Lyra geometry by means of
Duffin-Kemmer-Petiau (DKP) theory. Using Schwinger Variational Principle,
equations of motion, conservation laws and gauge symmetry are implemented. We
find that the scalar field couples to the anholonomic part of the torsion
tensor, and the gau... | 0509117v1 |
2005-11-17 | Late-time tail of a coupled scalar field in the background of a black hole with a global monopole | Using the technique of spectral decomposition, we investigated the late-time
tails of massless and massive coupled scalar fields in the background of a
black hole with a global monopole. We found that due to existence of the
coupling between the scalar and gravitational fields, the massless scalar field
decay faster at... | 0511098v2 |
2006-02-02 | Group field theory formulation of 3d quantum gravity coupled to matter fields | We present a new group field theory describing 3d Riemannian quantum gravity
coupled to matter fields for any choice of spin and mass. The perturbative
expansion of the partition function produces fat graphs colored with SU(2)
algebraic data, from which one can reconstruct at once a 3-dimensional
simplicial complex rep... | 0602010v1 |
2006-12-11 | Averaged Energy Inequalities for Non-Minimally Coupled Classical Scalar Fields | The stress-energy tensor for the non-minimally coupled scalar field is known
not to satisfy the pointwise energy conditions, even on the classical level. We
show, however, that local averages of the classical stress-energy tensor
satisfy certain inequalities and give bounds for averages along causal
geodesics. It is sh... | 0612064v1 |
2007-03-18 | Numerical simulations of gravitational collapse in Einstein-aether theory | We study gravitational collapse of a spherically symmetric scalar field in
Einstein-aether theory (general relativity coupled to a dynamical unit timelike
vector field). The initial value formulation is developed, and numerical
simulations are performed. The collapse produces regular, stationary black
holes, as long as... | 0703093v2 |
1998-03-03 | Limits on WWgamma and WWZ Couplings from W Boson Pair Production | The results of a search for W boson pair production in pbar-p collisions at
sqrt{s}=1.8 TeV with subsequent decay to emu, ee, and mumu channels are
presented. Five candidate events are observed with an expected background of
3.1+-0.4 events for an integrated luminosity of approximately 97 pb^{-1}.
Limits on the anomalo... | 9803004v1 |
1998-12-02 | Extended Modified Observable Technique for a Multi-Parametric Trilinear Gauge Coupling Estimation at LEP II | This paper describes the extension of the Modified Observables technique in
estimating simultaneously more than one Trilinear Gauge Couplings. The optimal
properties, unbiasedness and consistent error estimation of this method are
demonstrated by Monte Carlo experimentation using $\ell \nu jj $ four-fermion
final state... | 9812002v1 |
1999-03-12 | Recent QCD Results from LEP-1 and LEP-2 | A summary is given of some recent QCD results from LEP. For LEP-2, the topics
include event shape measurements, determinations of the strong coupling
constant, and measurements of the charged particle multiplicity distribution at
the recently completed run at 189 GeV. For LEP-1, the topics presented are a
test of the f... | 9903020v1 |
2000-08-15 | The strong coupling and the gluon density from jets in DIS | The extraction of the parameters of perturbative QCD is one of the main tasks
for the HERA experiments. Studies on the structure of the hadronic final states
with jet algorithms give a direct handle on the parton density functions and
the strong coupling strength over a wide kinematic range. In this article, new
result... | 0008027v1 |
2004-07-06 | Study of the e^+e^- --> Z gamma Process at LEP and Limits on Triple Neutral-Gauge-Boson Couplings | The process e^+e^- --> Z gamma, where the Z boson decays into hadrons or
neutrinos, is studied with data collected with the L3 detector at LEP at
centre-of-mass energies from 189 GeV up to 209 GeV. The cross sections are
measured and found to be in agreement with the Standard Model predictions.
Limits on triple neutral... | 0407012v1 |
1992-05-09 | Ising Model Coupled to Three-Dimensional Quantum Gravity | We have performed Monte Carlo simulations of the Ising model coupled to
three-dimensional quantum gravity based on a summation over dynamical
triangulations. These were done both in the microcanonical ensemble, with the
number of points in the triangulation and the number of Ising spins fixed, and
in the grand canoncal... | 9205009v1 |
1992-05-27 | Central Charge of the Parallelogram Lattice Strong Coupling Schwinger Model | We put forth a Fierzed hopping expansion for strong coupling Wilson fermions.
As an application, we show that the strong coupling Schwinger model on
parallelogram lattices with nonbacktracking Wilson fermions span, as a function
of the lattice skewness angle, the $\Delta = -1$ critical line of $6$-vertex
models. This F... | 9205026v1 |
1992-06-11 | The XY Model Coupled to Two-Dimensional Quantum Gravity | We perform Monte Carlo simulations using the Wolff cluster algorithm of the
XY model on both fixed and dynamical phi-cubed graphs (i.e. without and with
coupling to two-dimensional quantum gravity). We compare the numerical results
with the theoretical expectation that the phase transition remains of KT type
when the X... | 9206015v1 |
1992-07-06 | The Phase Diagram of a U(1) Higgs-Yukawa Model at Finite $λ$ | In this paper we investigate how the phase diagram of a U(1) symmetric
Higgs-Yukawa system depends on the scalar self coupling $\lambda$. The phase
diagram of similar models with continuous symmetry were extensively studied in
the infinite scalar self coupling $\lambda=\infty$ limit. Recent analytical and
numerical cal... | 9207006v1 |
1992-11-30 | Running Coupling in pure gauge theories using the Schrödinger functional | Schr\"odinger functional, the propagation kernel for going from some field
configuration at time $x^0=0$ to some other configuration at $x^0=T$, is used
to define a running coupling, $\bar g^2(L)$, at a length scale, $L$, in pure
gauge theories. Using a lattice formulation and finite size scaling techniques,
this runni... | 9211066v1 |
1993-01-20 | Does the 2d Higgs-Yukawa Model Have a Symmetric Phase at Small Yukawa Coupling Region? | We show that at arbitrary value of the scalar self coupling and small Yukawa
coupling $y$ the 2d Higgs-Yukawa model with Z(2) symmetry remains in the broken
phase and the model is asymptotically free: $y \to 0$ as the cut-off $\Lambda
\to \infty$. This is in agreement with a recent conjecture based on numerical
simulat... | 9301009v1 |
1993-11-05 | The Running Coupling From Lattice QCD | A recent lattice calculation of the QCD running coupling is presented. The
coupling is extracted from the force between two static quarks in the framework
of the valence quark approximation. A value of the Lambda-parameter for zero
quark flavours is determined: Lambda_msbar=0.630(38)\sqrt{\sigma}
=293(18)^{+25}_{-63} M... | 9311009v1 |
1993-11-30 | Non-perturbative investigation of the fermion-Higgs sector of the standard model | We present results for the renormalized quartic self-coupling $\lm_R$ and the
renormalized Yukawa coupling $y_R$ in a fermion-Higgs model with two SU(2)
doublets, indicating that with the standard lattice regulator these couplings
cannot become very strong. | 9311068v1 |
1994-01-03 | Hadronic coupling constants in lattice QCD | We report on calculations of the hadronic coupling constants $g_{\rho\pi\pi}$
and $g_{nn\pi}$ based on lattice QCD with four flavors of dynamical staggered
fermions. By computing 2--point and 3--point Green's functions we have been
able to determine these coupling constants ab initio from QCD; the results are
compatibl... | 9401001v2 |
1994-11-21 | Universal behaviour of the SU(2) running coupling constant in the continuum limit | We present data from the ALPHA Collaboration about lattice calculation of
SU(2) pure--gauge running coupling constant, obtained with two different
definitions of the coupling itself, which show universality of the continuum
limit and clarify the applicability of renormalized perturbation theory. | 9411035v2 |
1995-01-19 | Study of the Decoupling of Heavy Fermions in a Z_2 Scalar-Fermion Model | According to one-loop perturbation theory, fermions whose masses are totally
generated from Yukawa couplings do not decouple in the heavy mass limit. We
investigate this issue nonperturbatively in a 4-dimensional $Z_2$
scalar-fermion model with staggered fermions. Our data at intermediate and
stronger Yukawa couplings ... | 9501020v1 |
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