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47
1995-12-28
MSSM radiative contributions to the WW$γ$ and WWZ form factors
We evaluate one-loop contributions to the C and P conserving $WW\gamma, WWZ$ form factors in the Minimal Supersymmetric Standard Model (MSSM), and in a more constrained Supergravity Grand Unified Theory (SUGRA-GUT). A systematic search of maximal effects in the available parameter space, shows that at LEP2 energy MSSM ...
9512437v2
1998-07-10
Inverting the Supersymmetric Standard Model Spectrum: from Physical to Lagrangian Ino Parameters
We examine the possibility of recovering the supersymmetric (and soft supersymmetry breaking) Lagrangian parameters as direct {\em analytical} expressions of appropriate physical masses, for the unconstrained (but CP and R-parity conserving) minimal supersymmetric standard model. We concentrate mainly on the algebraica...
9807336v2
1999-07-01
A convergent scheme for one-loop evolutions of the Yukawa couplings in the MSSM
Integrated forms of the one-loop evolution equations are given for the Yukawa couplings in the MSSM, valid for any value of $\tan \beta$, generalizable to virtually any number of Yukawa fermions, and including all gauge couplings. These forms turn out to have nice mathematical convergence properties which we prove, and...
9907204v1
1999-07-14
Phases in the gaugino sector: direct reconstruction of the basic parameters and impact on the neutralino pair production
We consider recovering analytically the (generally complex) parameters $\mu$, $M_1$ and $M_2$ of the gaugino and Higgsino Lagrangian, from appropriate physical input in the chargino and neutralino sectors. For given $\tan\beta$, we obtain very simple analytic solutions for $M_2$, $| \mu|$, $Arg[\mu]$ in the chargino se...
9907360v1
1999-12-08
Analytical Study of Non-Universality of the Soft Terms in the MSSM
We obtain general analytical forms for the solutions of the one-loop renormalization group equations in the top/bottom/$\tau$ sector of the MSSM. These solutions are valid for any value of $\tan \beta$ as well as any non-universal initial conditions for the soft SUSY breaking parameters and non-unification of the Yukaw...
9912271v1
2001-01-22
General one-loop renormalization group evolutions and electroweak symmetry breaking in the (M+1)SSM
We study analytically the general features of electroweak symmetry breaking in the context of the Minimal Supersymmetric Standard Model extended by one Higgs singlet. The exact analytical forms of the renormalization group evolutions of the Yukawa couplings and of the soft supersymmetry breaking parameters are derived ...
0101237v1
2001-12-28
Infrared Quasi Fixed Point Structure in Extended Yukawa Sectors and Application to R-parity Violation
We investigate one-loop renormalization group evolutions of extended sectors of Yukawa type couplings. It is shown that Landau Poles which usually provide necessary low energy upper bounds that saturate quickly with increasing initial value conditions, lead in some cases to the opposite behaviour: some of the low energ...
0112353v1
2005-04-04
Natural gravitino dark matter in SO(10) gauge mediated supersymmetry breaking
It is shown that gravitinos with mass m_{3/2} ~ 0.1-1 MeV may provide suitable cold dark matter candidates in scenarios of gauge mediated supersymmetry breaking (GMSB) under SO(10) grand unification coupled to supergravity, which accommodate a messenger sector of mass scale M_X ~ 10^6 GeV. This is due to the combined e...
0504021v2
2005-06-14
Gravitino dark matter in gauge mediated supersymmetry breaking
This paper investigates the parameter space of theories with gauge mediated supersymmetry breaking leading to gravitino (cold) dark matter with mass m_{3/2}= 1keV - 10MeV. We pay particular attention to the cosmological role of messenger fields. Cosmology requires that these messengers decay to the visible sector if th...
0506129v2
1991-08-22
On the Perturbations of String-Theoretic Black Holes
The perturbations of string-theoretic black holes are analyzed by generalizing the method of Chandrasekhar. Attention is focussed on the case of the recently considered charged string-theoretic black hole solutions as a representative example. It is shown that string-intrinsic effects greatly alter the perturbed motion...
9108012v1
1992-10-31
All Or Nothing: On the Small Fluctuations of Two-Dimensional String-Theoretic Black Holes
A comprehensive analysis of small fluctuations about two-dimensional string-theoretic and string-inspired black holes is presented. It is shown with specific examples that two-dimensional black holes behave in a radically different way from all known black holes in four dimensions. For both the $SL(2,R)/U(1)$ black hol...
9210165v3
1993-04-01
Wavelet transforms versus Fourier transforms
This note is a very basic introduction to wavelets. It starts with an orthogonal basis of piecewise constant functions, constructed by dilation and translation. The ``wavelet transform'' maps each $f(x)$ to its coefficients with respect to this basis. The mathematics is simple and the transform is fast (faster than the...
9304214v1
1998-04-24
Enumeration of m-ary cacti
The purpose of this paper is to enumerate various classes of cyclically colored m-gonal plane cacti, called m-ary cacti. This combinatorial problem is motivated by the topological classification of complex polynomials having at most m critical values, studied by Zvonkin and others. We obtain explicit formulae for both ...
9804119v2
2002-08-21
Toric codes over finite fields
In this note, a class of error-correcting codes is associated to a toric variety associated to a fan defined over a finite field $\fff_q$, analogous to the class of Goppa codes associated to a curve. For such a ``toric code'' satisfying certain additional conditions, we present an efficient decoding algorithm for the d...
0208155v2
2002-12-05
Automorphisms of hyperbolic groups and graphs of groups
Using the canonical JSJ splitting, we describe the outer automorphism group $\Out(G)$ of a one-ended word hyperbolic group $G$. In particular, we discuss to what extent $\Out(G)$ is virtually a direct product of mapping class groups and a free abelian group, and we determine for which groups $\Out(G)$ is infinite. We a...
0212088v1
2004-06-08
The structure and labelled enumeration of K_{3,3}-subdivision-free projective-planar graphs
We consider the class F of 2-connected non-planar K_{3,3}-subdivision-free graphs that are embeddable in the projective plane. We show that these graphs admit a unique decomposition as a graph K_5 (the core) where the edges are replaced by two-pole networks constructed from 2-connected planar graphs. A method to enumer...
0406140v5
2004-09-16
Translation equivalence in free groups
Motivated by the work of Leininger on hyperbolic equivalence of homotopy classes of closed curves on surfaces, we investigate a similar phenomenon for free groups. Namely, we study the situation when two elements $g,h$ in a free group $F$ have the property that for every free isometric action of $F$ on an $\mathbb{R}$-...
0409284v2
2004-11-16
Characterization and enumeration of toroidal K_{3,3}-subdivision-free graphs
We describe the structure of 2-connected non-planar toroidal graphs with no K_{3,3}-subdivisions, using an appropriate substitution of planar networks into the edges of certain graphs called toroidal cores. The structural result is based on a refinement of the algorithmic results for graphs containing a fixed K_5-subdi...
0411356v1
2005-01-19
The outer space of a free product
We associate a contractible ``outer space'' to any free product of groups G=G_1*...*G_q. It equals Culler-Vogtmann space when G is free, McCullough-Miller space when no G_i is Z. Our proof of contractibility (given when G is not free) is based on Skora's idea of deforming morphisms between trees. Using the action of ...
0501288v3
2005-07-28
Free-group automorphisms, train tracks and the beaded decomposition
We study the automorphisms \phi of a finitely generated free group F. Building on the train-track technology of Bestvina, Feighn and Handel, we provide a topological representative f:G\to G of a power of \phi that behaves very much like the realization on the rose of a positive automorphism. This resemblance is encapsu...
0507589v2
2007-02-02
Line-of-sight percolation
Given $\omega\ge 1$, let $Z^2_{(\omega)}$ be the graph with vertex set $Z^2$ in which two vertices are joined if they agree in one coordinate and differ by at most $\omega$ in the other. (Thus $Z^2_{(1)}$ is precisely $Z^2$.) Let $p_c(\omega)$ be the critical probability for site percolation in $Z^2_{(\omega)}$. Extend...
0702061v2
2000-03-06
Entropy Production, Fractals, and Relaxation to Equilibrium
The theory of entropy production in nonequilibrium, Hamiltonian systems, previously described for steady states using partitions of phase space, is here extended to time dependent systems relaxing to equilibrium. We illustrate the main ideas by using a simple multibaker model, with some nonequilibrium initial state, an...
0003012v2
2002-03-21
Entropy production of diffusion in spatially periodic deterministic systems
This paper presents an {\it ab initio} derivation of the expression given by irreversible thermodynamics for the rate of entropy production for different classes of diffusive processes. The first class are Lorentz gases, where non-interacting particles move on a spatially periodic lattice, and collide elastically with ...
0203046v1
2001-11-09
Spatial diffusion in a periodic optical lattice: revisiting the Sisyphus effect
We numerically study the spatial diffusion of an atomic cloud experiencing Sisyphus cooling in a three-dimensional lin$\bot$lin optical lattice in a broad range of lattice parameters. In particular, we investigate the dependence on the size of the lattice sites which changes with the angle between the laser beams. We s...
0111070v2
2006-07-24
Use of specific Green's functions for solving direct problems involving a heterogeneous rigid frame porous medium slab solicited by acoustic waves
A domain integral method employing a specific Green's function (i.e., incorporating some features of the global problem of wave propagation in an inhomogeneous medium) is developed for solving direct and inverse scattering problems relative to slab-like macroscopically inhomogeneous porous obstacles. It is shown how to...
0607212v1
2005-12-12
Cloning, expression and purification of the general stress protein Yhbo from Escherichia coli
We cloned, expressed and purified the Escherichia coli yhbO gene product, which is homolog to the Bacillus subtilis general stress protein 18 (the yfkM gene product), the Pyrococcus furiosus intracellular protease PfpI, and the human Parkinson disease protein DJ-1. The gene coding for YhbO was generated by amplifying t...
0512028v1
2003-01-24
Rayleigh Scattering and Atomic Dynamics in Dissipative Optical Lattices
We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals (S. Guibal {\it et al}, Phys. Rev. Lett. {\bf 78}, 4709 (1997); C. Jurczak {\it et al}, Phys. Rev. Lett. {\bf 77}, 1727 (1996)), we study whether the Rayleigh resonance originates from the diffraction on a dens...
0301139v1
2005-12-19
More on the Asymmetric Infinite Square Well: Energy Eigenstates with Zero Curvature
We extend the standard treatment of the asymmetric infinite square well to include solutions that have zero curvature over part of the well. This type of solution, both within the specific context of the asymmetric infinite square well and within the broader context of bound states of arbitrary piecewise-constant poten...
0512156v1
2006-05-09
Communicating over adversarial quantum channels using quantum list codes
We study quantum communication in the presence of adversarial noise. In this setting, communicating with perfect fidelity requires using a quantum code of bounded minimum distance, for which the best known rates are given by the quantum Gilbert-Varshamov (QGV) bound. By asking only for arbitrarily high fidelity and all...
0605086v2
2007-05-16
Quantization Bounds on Grassmann Manifolds of Arbitrary Dimensions and MIMO Communications with Feedback
This paper considers the quantization problem on the Grassmann manifold with dimension n and p. The unique contribution is the derivation of a closed-form formula for the volume of a metric ball in the Grassmann manifold when the radius is sufficiently small. This volume formula holds for Grassmann manifolds with arbit...
0705.2272v1
2007-05-24
Local spin dynamic arising from the non-perturbative SU(2) gauge field of the spin orbit effect
We use the non-perturbative gauge field approach to study the effects of spin orbit coupling on the dynamic of magnetic moment. We present a general equation of motion (EOM) which unifies i) the spin orbit coupling effect derived from the SU(2) spin gauge field, and ii) the moment chirality effect previously derived fr...
0705.3502v1
2007-06-07
$^{77}$Se NMR measurements of the $π-d$ exchange field in the organic conductor $λ-$(BETS)$_{2}$FeCl$_{4}$
$^{77}$Se-NMR spectrum and frequency shift measurements in the paramagnetic metal (PM) and antiferromagnetic insulating (AFI) phases are reported for a small single crystal of the organic conductor $\lambda-$(BETS)$_{2}$FeCl$_{4}$ as a function of temperature ($T$) and field alignment for an applied magnetic field $B_{...
0706.0933v1
2007-11-05
Feedback Capacity of the Compound Channel
In this work we find the capacity of a compound finite-state channel with time-invariant deterministic feedback. The model we consider involves the use of fixed length block codes. Our achievability result includes a proof of the existence of a universal decoder for the family of finite-state channels with feedback. As...
0711.0705v1
2007-11-12
Mutual phase-locking in high frequency microwave nanooscillators as function of field angle
We perform a qualitative analysis of phase locking in a double point-contact spinvalve system by solving the Landau-Lifshitz-Gilbert-Slonzewski equation using a hybrid-finite-element method. We show that the phase-locking behaviour depends on the applied field angle. Starting from a low field angle, the locking-current...
0711.1770v2
2007-11-14
Emergent singular solutions of non-local density-magnetization equations in one dimension
We investigate the emergence of singular solutions in a non-local model for a magnetic system. We study a modified Gilbert-type equation for the magnetization vector and find that the evolution depends strongly on the length scales of the non-local effects. We pass to a coupled density-magnetization model and perform a...
0711.2177v1
2007-11-27
Nonequilibrium interacting electrons in a ferromagnet
Dynamics of the magnetization in ferromagnets is examined in the presence of transport electrons allowing the latter to interact. It is found that the existence of inhomogeneities such as domain wall (DW) structures, leads to changes that affect the dynamical structure of the equations of motion for the magnetization. ...
0711.4170v2
2007-12-01
On Precision - Redundancy Relation in the Design of Source Coding Algorithms
We study the effects of finite-precision representation of source's probabilities on the efficiency of classic source coding algorithms, such as Shannon, Gilbert-Moore, or arithmetic codes. In particular, we establish the following simple connection between the redundancy $R$ and the number of bits $W$ necessary for re...
0712.0057v1
2007-12-03
Kinetic models of heterogeneous dissipation
We suggest kinetic models of dissipation for an ensemble of interacting oriented particles, for example, moving magnetized particles. This is achieved by introducing a double bracket dissipation in kinetic equations using an oriented Poisson bracket, and employing the moment method to derive continuum equations for mag...
0712.0397v1
2007-12-13
Euler equation of the optimal trajectory for the fastest magnetization reversal of nano-magnetic structures
Based on the modified Landau-Lifshitz-Gilbert equation for an arbitrary Stoner particle under an external magnetic field and a spin-polarized electric current, differential equations for the optimal reversal trajectory, along which the magnetization reversal is the fastest one among all possible reversal routes, are ob...
0712.2101v1
2007-12-18
Effect of Edge Roughness on Electronic Transport in Graphene Nanoribbon Channel Metal Oxide Semiconductor Field-Effect Transistors
Results of quantum mechanical simulations of the influence of edge disorder on transport in graphene nanoribbon metal oxide semiconductor field-effect transistors (MOSFETs) are reported. The addition of edge disorder significantly reduces ON-state currents and increases OFF-state currents, and introduces wide variabili...
0712.3068v1
2007-12-22
Explicit Non-Adaptive Combinatorial Group Testing Schemes
Group testing is a long studied problem in combinatorics: A small set of $r$ ill people should be identified out of the whole ($n$ people) by using only queries (tests) of the form "Does set X contain an ill human?". In this paper we provide an explicit construction of a testing scheme which is better (smaller) than an...
0712.3876v5
2007-12-31
Risk management for analytical methods: conciliating objectives of methods, validation phase and routine decision rules
In the industries that involved either chemistry or biology, such as pharmaceutical industries, chemical industries or food industry, the analytical methods are the necessary eyes and hear of all the material produced or used. If the quality of an analytical method is doubtful, then the whole set of decision that will ...
0801.0207v1
2008-01-06
An Efficient Method for Quantum Transport Calculations in Nanostructures using Full Band Structure
Scaling of semiconductor devices has reached a stage where it has become absolutely imperative to consider the quantum mechanical aspects of transport in these ultra small devices. In these simulations, often one excludes a rigorous band structure treatment, since it poses a huge computational challenge. We have propos...
0801.0880v1
2008-01-07
Magnetization reversal driven by spin-injection : a mesoscopic spin-transfer effect
A mesoscopic description of spin-transfer effect is proposed, based on the spin-injection mechanism occurring at the junction with a ferromagnet. The effect of spin-injection is to modify locally, in the ferromagnetic configuration space, the density of magnetic moments. The corresponding gradient leads to a current-de...
0801.1019v1
2008-01-25
New Lower Bounds on Sizes of Permutation Arrays
A permutation array(or code) of length $n$ and distance $d$, denoted by $(n,d)$ PA, is a set of permutations $C$ from some fixed set of $n$ elements such that the Hamming distance between distinct members $\mathbf{x},\mathbf{y}\in C$ is at least $d$. Let $P(n,d)$ denote the maximum size of an $(n,d)$ PA. This correspon...
0801.3986v1
2008-01-30
Femtosecond Control of the Magnetization in Ferromagnetic Semiconductors
We develop a theory of collective spin dynamics triggered by ultrafast optical excitation of ferromagnetic semiconductors. Using the density matrix equations of motion in the mean field approximation and including magnetic anisotropy and hole spin dephasing effects, we predict the development of a light--induced magnet...
0801.4641v1
2008-02-01
Vortex Ferroelectric Domains
We show experimental switching data on microscale capacitors of lead-zirconate-titanate (PZT), which reveal time-resolved domain behavior during switching on a 100-ns scale. For small circular capacitors, an unswitched domain remains in the center while complete switching is observed in square capacitors. The observed ...
0802.0186v1
2008-02-11
Structure and Optimality of Myopic Policy in Opportunistic Access with Noisy Observations
A restless multi-armed bandit problem that arises in multichannel opportunistic communications is considered, where channels are modeled as independent and identical Gilbert-Elliot channels and channel state observations are subject to errors. A simple structure of the myopic policy is established under a certain condi...
0802.1379v2
2008-02-12
Domain walls in (Ga,Mn)As diluted magnetic semiconductor
We report experimental and theoretical studies of magnetic domain walls in an in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our high-resolution electron holography technique provides direct images of domain wall magnetization profiles. The experiments are interpreted based on microscopic calc...
0802.1574v1
2008-02-21
Solving functional reliability issue for an optical electrostatic switch
In this paper, we report the advantage of using AC actuating signal for driving MEMS actuators instead of DC voltages. The study is based upon micro mirror devices used in digital mode for optical switching operation. When the pull-in effect is used, charge injection occurs when the micro mirror is maintained in the de...
0802.3075v1
2008-02-21
First principles calculation of spin-interactions and magnetic ground states of Cr trimers on Au(111)
We present calculations of the magnetic ground states of Cr trimers in different geometries on top of a Au(111) surface. By using a least square fit method based on a fully relativistic embedded-cluster Green's function method first we determined the parameters of a classical vector-spin model consisting of second and ...
0802.3113v1
2008-04-07
Energy equilibriation processes of electrons, magnons and phonons on the femtosecond timescale
By means of time-resolved Kerr spectroscopy experiments we relate the energy dissipation processes on the femtosecond (electron-spin relaxation time $\tau_{el-sp}$) and nanosecond timescale (Gilbert relaxation $\tau_{\alpha}$) and compare the results to the first microscopic model, which was proposed by Koopmans. For b...
0804.0985v1
2008-04-07
Woven Graph Codes: Asymptotic Performances and Examples
Constructions of woven graph codes based on constituent block and convolutional codes are studied. It is shown that within the random ensemble of such codes based on $s$-partite, $s$-uniform hypergraphs, where $s$ depends only on the code rate, there exist codes satisfying the Varshamov-Gilbert (VG) and the Costello lo...
0804.0996v2
2008-05-26
Photometric Follow-up Observations of the Transiting Neptune-Mass Planet GJ 436b
This paper presents multi-band photometric follow-up observations of the Neptune-mass transiting planet GJ 436b, consisting of 5 new ground-based transit light curves obtained in May 2007. Together with one already published light curve we have at hand a total of 6 light curves, spanning 29 days. The analysis of the da...
0805.3915v2
2008-06-04
Broadband electrical detection of spin excitations in (Ga,Mn)As using a photovoltage technique
We report on microwave photovoltage and simultaneous magnetotransport measurements in a (Ga,Mn)As film oriented normal to the magnetic field. We detect the ferromagnetic resonance over a broad frequency range of 2 GHz to 18.5 GHz and determine the spectroscopic g-factor and separate the Gilbert from the inhomogeneous c...
0806.0785v1
2008-07-10
Mechanical and Electronic Properties of Ferromagnetic GaMnAs Using Ultrafast Coherent Acoustic Phonons
Ultrafast two-color pump-probe measurements, involving coherent acoustic phonon (CAP) waves, have provided information simultaneously on the mechanical properties and on the electronic structure of ferromagnetic GaMnAs. The elastic constant C11 of Ga1-xMnxAs (0.03<x<0.07) are observed to be systematically smaller than ...
0807.1740v2
2008-08-05
A Proof of George Andrews' and Dave Robbins' q-TSPP Conjecture (modulo a finite amount of routine calculations)
In the historic conference Combinatoire Enumerative[LL] wonderfully organized by Gilbert Labelle and Pierre Leroux there were many stimulating lectures, including a very interesting one by Pierre Leroux himself, who talked about his joint work with Xavier Viennot[LV], on solving differential equations combinatorially! ...
0808.0571v2
2008-08-09
On some deterministic dictionaries supporting sparsity
We describe a new construction of an incoherent dictionary, referred to as the oscillator dictionary, which is based on considerations in the representation theory of finite groups. The oscillator dictionary consists of order of p^5 unit vectors in a Hilbert space of dimension p, where p is an odd prime, whose pairwise...
0808.1368v2
2008-08-13
Spin Filter, Spin Amplifier and Other Spintronic Applications in Graphene Nanodisks
Graphene nanodisk is a graphene derivative with a closed edge. The trigonal zigzag nanodisk with size $N$ has $N$-fold degenerated zero-energy states. A nanodisk can be interpletted as a quantum dot with an internal degree of freedom. The grand state of nanodisk has been argued to be a quasi-ferromagnet, which is a fer...
0808.1779v1
2008-08-26
Codes on hypergraphs
Codes on hypergraphs are an extension of the well-studied family of codes on bipartite graphs. Bilu and Hoory (2004) constructed an explicit family of codes on regular t-partite hypergraphs whose minimum distance improves earlier estimates of the distance of bipartite-graph codes. They also suggested a decoding algorit...
0808.3453v2
2008-09-26
Ultra-fast spin dynamics: the effect of colored noise
Recent experimental results have pushed the limits of magnetization dynamics to pico- and femtosecond timescales. This ultra-fast spin dynamics occurs in extreme conditions of strong and rapidly varying fields and high temperatures. This situation requires new description of magnetization dynamics, even on a phenomenol...
0809.4595v1
2008-10-08
Magnetic particle hyperthermia: Neel relaxation in magnetic nanoparticles under circularly polarized field
The mechanism of magnetization reversal in single-domain ferromagnetic particles is of interest in many applications, in most of which losses must be minimized. In cancer therapy by hyperthermia the opposite requirement prevails: the specific loss power should be maximized. Of the mechanisms of dissipation, here we stu...
0810.1455v2
2008-10-10
SOSEMANUK: a fast software-oriented stream cipher
Sosemanuk is a new synchronous software-oriented stream cipher, corresponding to Profile 1 of the ECRYPT call for stream cipher primitives. Its key length is variable between 128 and 256 bits. It ac- commodates a 128-bit initial value. Any key length is claimed to achieve 128-bit security. The Sosemanuk cipher uses bot...
0810.1858v1
2008-11-14
Trees of cylinders and canonical splittings
Let T be a tree with an action of a finitely generated group G. Given a suitable equivalence relation on the set of edge stabilizers of T (such as commensurability, co-elementarity in a relatively hyperbolic group, or commutation in a commutative transitive group), we define a tree of cylinders T_c. This tree only depe...
0811.2383v2
2008-11-21
Numerical Study of Current-Induced Domain-Wall Dynamics: Crossover from Spin Transfer to Momentum Transfer
We study current-induced dynamics of a magnetic domain wall by solving a time-dependent Schr\"{o}dinger equation combined with Landau-Lifshitz-Gilbert equation in a one-dimensional electron system coupled to localized spins. Two types of domain-wall motions are observed depending on the hard-axis anisotropy, $K_{\perp}...
0811.3545v2
2008-12-02
Application of Conformal Mapping to the determination of Magnetic Moment Distributions in typical Antidot Film Nanostructures
There has been an increasing technological interest on magnetic thin films containing antidot arrays of hexagonal or square symmetry. Part of this interest is related to the possibility of domain formation and pinning at the antidots boundaries. In this paper, we develop a method for the calculation of the magnetic mom...
0812.0566v1
2009-01-09
A Better Way to Deal the Cards
This paper considers the effect of riffle shuffling on decks of cards, allowing for some cards to be indistinguishable from other cards. The dual problem of dealing a game with hands, such as bridge or poker, is also considered. The Gilbert-Shannon-Reeds model of card shuffling is used, along with variation distance fo...
0901.1324v4
2009-03-12
Accuracy thresholds of topological color codes on the hexagonal and square-octagonal lattices
Accuracy thresholds of quantum error correcting codes, which exploit topological properties of systems, defined on two different arrangements of qubits are predicted. We study the topological color codes on the hexagonal lattice and on the square-octagonal lattice by the use of mapping into the spin glass systems. The ...
0903.2102v5
2009-03-12
Designing Optimal Flow Networks
We investigate the problem of designing a minimum cost flow network interconnecting n sources and a single sink, each with known locations and flows. The network may contain other unprescribed nodes, known as Steiner points. For concave increasing cost functions, a minimum cost network of this sort has a tree topology,...
0903.2124v1
2009-04-13
Refined Coding Bounds and Code Constructions for Coherent Network Error Correction
Coherent network error correction is the error-control problem in network coding with the knowledge of the network codes at the source and sink nodes. With respect to a given set of local encoding kernels defining a linear network code, we obtain refined versions of the Hamming bound, the Singleton bound and the Gilber...
0904.1897v2
2009-04-27
Effect of resistance feedback on spin torque-induced switching of nanomagnets
In large magnetoresistance devices spin torque-induced changes in resistance can produce GHz current and voltage oscillations which can affect magnetization reversal. In addition, capacitive shunting in large resistance devices can further reduce the current, adversely affecting spin torque switching. Here, we simultan...
0904.4159v2
2009-04-30
A microscopic model for current-induced switching of magnetization for half-metallic leads
We study the behaviour of the magnetization in a half-metallic ferromagnet/nonmagnetic insulator/ferromagnetic metal/paramagnetic metal (FM1/NI/FM2/PM) tunnel junction. It is calculated self-consistently within the nonequilibrium Keldysh formalism. The magnetic regions are treated as band ferromagnets and are described...
0904.4821v1
2009-05-26
Scattering Theory of Charge-Current Induced Magnetization Dynamics
In ferromagnets, charge currents can excite magnons via the spin-orbit coupling. We develop a novel and general scattering theory of charge current induced macrospin magnetization torques in normal metal$|$ferromagnet$|$normal metal layers. We apply the formalism to a dirty GaAs$|$(Ga,Mn)As$|$GaAs system. By computing ...
0905.4170v2
2009-05-28
Riffle shuffles of a deck with repeated cards
We study the Gilbert-Shannon-Reeds model for riffle shuffles and ask 'How many times must a deck of cards be shuffled for the deck to be in close to random order?'. In 1992, Bayer and Diaconis gave a solution which gives exact and asymptotic results for all decks of practical interest, e.g. a deck of 52 cards. But wh...
0905.4698v1
2009-07-20
Correcting Limited-Magnitude Errors in the Rank-Modulation Scheme
We study error-correcting codes for permutations under the infinity norm, motivated by a novel storage scheme for flash memories call rank modulation. In this scheme, a set of $n$ flash cells are combined to create a single virtual multi-level cell. Information is stored in the permutation induced by the cell charge le...
0907.3387v2
2009-07-22
Searching for variable stars in Galactic Open Clusters
A long-term project, aiming at systematic search for variable stars in Galactic Open Clusters, was started at the Geneva Observatory in 2002. We have been observing regularly a sample of twenty-seven Galactic Open Clusters in the U, B, V Geneva filters. The goal is to identify and to study their variable stars, as well...
0907.3834v1
2009-07-23
Variability morphologies in the color-magnitude diagram. Searching for secular variability
This work is part of an effort to detect secular variable objects in large scale surveys by analysing their path in color-magnitude diagrams. To this aim, we first present the variability morphologies in the V/V-I diagram of several types of variable stars. They comprise both periodic and non periodic variable stars fr...
0907.4090v1
2009-08-03
Regret Bounds for Opportunistic Channel Access
We consider the task of opportunistic channel access in a primary system composed of independent Gilbert-Elliot channels where the secondary (or opportunistic) user does not dispose of a priori information regarding the statistical characteristics of the system. It is shown that this problem may be cast into the framew...
0908.0319v1
2009-08-14
Non-Gaussian Scatter in Cluster Scaling Relations
We investigate the impact of non-Gaussian scatter in the cluster mass-observable scaling relation on the mass and redshift distribution of clusters detected by wide area surveys. We parameterize non-Gaussian scatter by incorporating the third and forth moments (skewness and kurtosis) into the distribution P(Mobs|M). We...
0908.1978v1
2009-08-17
A local moment approach to the degenerate Anderson impurity model
The local moment approach is extended to the orbitally-degenerate [SU(2N)] Anderson impurity model (AIM). Single-particle dynamics are obtained over the full range of energy scales, focussing here on particle-hole symmetry in the strongly correlated regime where the onsite Coulomb interaction leads to many-body Kondo p...
0908.2245v1
2009-10-20
Bifurcation and chaos in spin-valve pillars in a periodic applied magnetic field
We study the bifurcation and chaos scenario of the macro-magnetization vector in a homogeneous nanoscale-ferromagnetic thin film of the type used in spin-valve pillars. The underlying dynamics is described by a generalized Landau-Lifshitz-Gilbert (LLG) equation. The LLG equation has an especially appealing form under a...
0910.3776v1
2009-12-08
Evidence of superconductivity on the border of quasi-2D ferromagnetism in Ca2RuO4 at high pressure
The layered perovskite Ca2RuO4 is a spin-one Mott insulator at ambient pressure and exhibits metallic ferromagnetism at least up to ~ 80 kbar with a maximum Curie temperature of 28 K. Above ~ 90 kbar and up to 140 kbar, the highest pressure reached, the resistivity and ac susceptibility show pronounced downturns below ...
0912.1513v1
2010-02-24
JSJ decompositions: definitions, existence, uniqueness. II. Compatibility and acylindricity
This paper and its companion arXiv:0911.3173 have been replaced by arXiv:1602.05139. We define the compatibility JSJ tree of a group G over a class of subgroups. It exists whenever G is finitely presented and leads to a canonical tree (not a deformation space) which is invariant under automorphisms. Under acylindrici...
1002.4564v3
2010-03-05
Magnetoresistance in nanostructures: the role of nonuniform current
We developed a method to calculate the magnetoresistance of magnetic nanostructures. We discretize a magnetic disk in small cells and numerically solve the Landau-Lifshitz-Gilbert (LLG) equation in order to obtain its magnetization profile. We consider a anisotropic magnetoresistance (AMR) that depends on the local mag...
1003.1323v2
2010-03-21
Current-induced domain wall motion with adiabatic spin torque only in cylindrical nanowires
We investigate current-driven domain wall (DW) propagation in magnetic nanowires in the framework of the modified Landau-Lifshitz-Gilbert equation with both adiabatic and nonadiabatic spin torque (NAST) terms. Contrary to the common opinion that NAST is indispensable for DW motion[1,2], we point out that adiabatic spin...
1003.3976v1
2010-04-01
Multipliers of locally compact quantum groups via Hilbert C$^*$-modules
A result of Gilbert shows that every completely bounded multiplier $f$ of the Fourier algebra $A(G)$ arises from a pair of bounded continuous maps $\alpha,\beta:G \rightarrow K$, where $K$ is a Hilbert space, and $f(s^{-1}t) = (\beta(t)|\alpha(s))$ for all $s,t\in G$. We recast this in terms of adjointable operators ac...
1004.0215v3
2010-04-22
Optimal time-dependent polarized current pattern for fast domain wall propagation in nanowires: Exact solutions for biaxial and uniaxial anisotropies
One of the important issues in nanomagnetism is to lower the current needed for a technologically useful domain wall (DW) propagation speed. Based on the modified Landau-Lifshitz-Gilbert (LLG) equation with both Slonczewski spin-transfer torque and the field-like torque, we derive the optimal spin current pattern for f...
1004.3840v1
2010-05-03
Criticality of an isotropic-to-smectic transition induced by anisotropic quenched disorder
We report combined optical birefringence and neutron scattering measurements on the liquid crystal 12CB nanoconfined in mesoporous silicon layers. This liquid crystal exhibits strong nematic-smectic coupling responsible for a discontinuous isotropic-to-smectic phase transition in the bulk state. Confined in porous sili...
1005.0240v1
2010-05-21
A Study on Potential of Integrating Multimodal Interaction into Musical Conducting Education
With the rapid development of computer technology, computer music has begun to appear in the laboratory. Many potential utility of computer music is gradually increasing. The purpose of this paper is attempted to analyze the possibility of integrating multimodal interaction such as vision-based hand gesture and speech ...
1005.4014v1
2010-05-28
Dissipative structures in a nonlinear dynamo
This paper considers magnetic field generation by a fluid flow in a system referred to as the Archontis dynamo: a steady nonlinear magnetohydrodynamic (MHD) state is driven by a prescribed body force. The field and flow become almost equal and dissipation is concentrated in cigar-like structures centred on straight-lin...
1005.5259v2
2010-06-11
Spherical single-roll dynamos at large magnetic Reynolds numbers
This paper concerns kinematic helical dynamos in a spherical fluid body surrounded by an insulator. In particular, we examine their behaviour in the regime of large magnetic Reynolds number $\Rm$, for which dynamo action is usually concentrated upon a simple resonant stream-surface. The dynamo eigensolutions are comput...
1006.2308v2
2010-06-11
On the Queueing Behavior of Random Codes over a Gilbert-Elliot Erasure Channel
This paper considers the queueing performance of a system that transmits coded data over a time-varying erasure channel. In our model, the queue length and channel state together form a Markov chain that depends on the system parameters. This gives a framework that allows a rigorous analysis of the queue as a function ...
1006.2403v1
2010-06-16
Storing Small Photonic Cluster States in a Dephasing Environment
We consider the effects of decoherence on the entanglement of photonic cluster states. Large photonic cluster states can be built by fusing together smaller photonic cluster states via probabilistic fusion operations. For this construction process it is necessary to store these smaller cluster states in some way so as ...
1006.3192v1
2010-08-05
Subsystem codes with spatially local generators
We study subsystem codes whose gauge group has local generators in the 2D geometry. It is shown that there exists a family of such codes defined on lattices of size LxL with the number of logical qubits k and the minimum distance d both proportional to L. The gauge group of these codes involves only two-qubit generator...
1008.1029v1
2010-08-14
Escape of resources in distributed clustering processes
In a distributed clustering algorithm introduced by Coffman, Courtois, Gilbert and Piret \cite{coffman91}, each vertex of $\mathbb{Z}^d$ receives an initial amount of a resource, and, at each iteration, transfers all of its resource to the neighboring vertex which currently holds the maximum amount of resource. In \cit...
1008.2426v1
2010-08-25
The self-avoiding walk in a strip
We review the existence of the infinite length self-avoiding walk in the half plane and its relationship to bridges. We prove that this probability measure is also given by the limit as $\beta \rightarrow \beta_c-$ of the probability measure on all finite length walks $\omega$ with the probability of $\omega$ proportio...
1008.4321v2
2010-08-29
Chirality control via double vortices in asymmetric Co dots
Reproducible control of the magnetic vortex state in nanomagnets is of critical importance. We report on chirality control by manipulating the size and/or thickness of asymmetric Co dots. Below a critical diameter and/or thickness, chirality control is achieved by the nucleation of single vortex. Interestingly, above t...
1008.4963v2
2010-09-18
Composite excitation of Josephson phase and spin waves in Josephson junctions with ferromagnetic insulator
Coupling of Josephson-phase and spin-waves is theoretically studied in a superconductor/ferromagnetic insulator/superconductor (S/FI/S) junction. Electromagnetic (EM) field inside the junction and the Josephson current coupled with spin-waves in FI are calculated by combining Maxwell and Landau-Lifshitz-Gilbert equatio...
1009.3551v3
2010-09-21
On the Flow-Level Delay of a Spatial Multiplexing MIMO Wireless Channel
The MIMO wireless channel offers a rich ground for quality of service analysis. In this work, we present a stochastic network calculus analysis of a MIMO system, operating in spatial multiplexing mode, using moment generating functions (MGF). We quantify the spatial multiplexing gain, achieved through multiple antennas...
1009.4091v1
2010-09-22
Optimal control of magnetization dynamics in ferromagnetic heterostructures by spin--polarized currents
We study the switching-process of the magnetization in a ferromagnetic-normal-metal multilayer system by a spin polarized electrical current via the spin transfer torque. We use a spin drift-diffusion equation (SDDE) and the Landau-Lifshitz-Gilbert equation (LLGE) to capture the coupled dynamics of the spin density and...
1009.4296v2