publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2005-01-27 | Dynamics of Quintessence with Thermal Interactions | The cosmological dynamics of minimally coupled scalar field that couple to
the background matter with thermal interactions is investigated in exponential
potential. The conditions for the existence and stability of various critical
points as well as their cosmological implications are obtained. Although we
show that th... | 0501596v2 |
2005-03-03 | Coupled Quintessence in a Power-Law Case and the Cosmic Coincidence Problem | The problem of the cosmic coincidence is a longstanding puzzle. This
conundrum may be solved by introducing a coupling between the two dark sectors.
In this Letter, we study a coupled quintessence scenario in which the scalar
field evolves in a power law potential and the mass of dark matter particles
depends on a powe... | 0503072v2 |
2005-04-10 | Anisotropic cosmological models with non-minimally coupled magnetic field | Motivated by the structure of one-loop vacuum polarization effects in curved
spacetime we discuss a non-minimal extension of the Einstein-Maxwell equations.
This formalism is applied to Bianchi I models with magnetic field. We obtain
several exact solutions of the non-minimal system including those which
describe an is... | 0504228v1 |
2005-05-10 | Inflationary Solutions in Nonminimally Coupled Scalar Field Theory | We study analytically and numerically the inflationary solutions for various
type scalar potentials in the nonminimally coupled scalar field theory. The
Hamilton-Jacobi equation is used to deal with nonlinear evolutions of
inhomogeneous spacetimes and the long-wavelength approximation is employed. The
constraints that ... | 0505188v1 |
2005-12-06 | Polarization transfer in pulsar magnetosphere | Propagation of radio waves in the ultrarelativistic magnetized
electron-positron plasma of pulsar magnetosphere is considered. Polarization
state of the original natural waves is found to vary markedly on account of the
wave mode coupling and cyclotron absorption. The change is most pronounced when
the regions of mode ... | 0512140v1 |
2005-12-06 | Evading the astrophysical limits on light pseudoscalars | We study the possibility of evading astrophysical bounds on light
pseudoscalars. We argue that the solar bounds can be evaded if we have a
sufficiently strong self coupling of the pseudoscalars. The required couplings
do not conflict with any known experimental bounds. We show that it is possible
to find a coupling ran... | 0512155v4 |
2006-06-30 | Tight coupling expansion and fully inhomogeneous magnetic fields | The tight coupling expansion, appropriately generalized to include
large-scale magnetic fields, allows the estimate of the brightness
perturbations of CMB anisotropies for typical wavelengths that are larger than
the Hubble radius after matter-radiation equality. After discussing the basic
features of the the pre-decou... | 0606759v1 |
2006-08-24 | Gravitational scalar field coupled directly to the Maxwell field and its effect to solar-system experiments | The effect of the massless gravitational scalar field assumed to couple
directly to the Maxwell field to the solar-system experiments is estimated. We
start with discussing the theoretical significances of this coupling. Rather
disappointingly, however, we find that the scalar-field parameters never affect
the observat... | 0608508v2 |
1996-03-15 | Quantum Reservoir Engineering | We show how to design different couplings between a single ion trapped in a
harmonic potential and an environment. This will provide the basis for the
experimental study of the process of decoherence in a quantum system. The
coupling is due to the absorption of a laser photon and subsequent spontaneous
emission. The va... | 9603002v1 |
1995-10-02 | Infinite dimensional SRB measures | We review the basic steps leading to the construction of a Sinai-Ruelle-Bowen
(SRB) measure for an infinite lattice of weakly coupled expanding circle maps,
and we show that this measure has exponential decay of space-time correlations.
First, using the Perron-Frobenius operator, one connects the dynamical system
of co... | 9509022v1 |
1995-12-28 | Folded Bifurcation in Coupled Asymmetric Logistic Maps | A system of coupled two logistic maps, one periodic and the other chaotic, is
studied. It is found that with the variation of the coupling strength, the
system displays several curious features such as the appearance of quadrupling
of period, occurrence of isolated period three attractor and the coexistence of
the Hopf... | 9512007v1 |
1996-01-19 | Nonadiabatic couplings and incipience of quantum chaos | The quantization of the electronic two site system interacting with a
vibration is considered by using as the integrable reference system the
decoupled oscillators resulting from the adiabatic approximation. A specific
Bloch projection method is applied which demonstrates how besides some regular
regions in the fine st... | 9601014v1 |
1996-04-29 | Heterogeneity Induced Order in Globally Coupled Chaotic Systems | Collective behavior is studied in globally coupled maps with distributed
nonlinearity. It is shown that the heterogeneity enhances regularity in the
collective dynamics. Low-dimensional quasiperiodic motion is often found for
the mean-field, even if each element shows chaotic dynamics. The mechanism of
this order is du... | 9604016v1 |
1996-07-29 | Limit Set of Trajectories of the Coupled Viscous Burgers' Equations | In this letter, a coupled system of viscous Burgers' equations with zero
Dirichlet boundary conditions and appropriate initial data is considered. For
the well-known single viscous Burgers' equation with zero Dirichlet boundary
conditions, the zero equilibrium is the unique global exponential point
attractor. A similar... | 9607016v1 |
1996-12-27 | Clustering dynamics in globally coupled map lattices | Clustering bifurcations are investigated by considering models of globally
coupled map lattices. Typical classes of clustering bifurcations are revealed.
The clustering bifurcation thresholds of the coupled system are closely related
to the bifurcation structures of single map. In particular, cluster-doubling
bifurcati... | 9701001v1 |
1997-10-14 | Stochastic Response, Cascading and Control of Colored Noise in Dynamical System | We analytically determine the correlation functions of the stochastic
response of a generic mapping system driven by colored noise. We also address
the issue of noise cascading in coupled-element systems, particularly in a
uni-directionally coupled system with dc-filtered coupling. A noise-feedback
method and an opposi... | 9710008v1 |
1997-11-13 | Analytical Approach for Piecewise Linear Coupled Map Lattices | A simple construction is presented, which generalises piecewise linear
one-dimensional Markov maps to an arbitrary number of dimensions. The
corresponding coupled map lattice, known as a simplicial mapping in the
mathematical literature, allows for an analytical investigation. Especially the
spin Hamiltonian, which is ... | 9711014v1 |
1997-11-21 | Spontaneous Decoherence in Coupled Quantum Kicked Rotators | Quantum mechanical behavior of coupled N-kicked rotators is studied. In the
large N limit each rotator evolves under influence of the mean-field generated
by surrounding rotators. It is found that the system spontaneously generates
classical chaos in the large N limit when the system parameter exceeds a
critical value.... | 9711021v1 |
1998-02-25 | Kolmogorov-Arnold-Moser--Renormalization-Group Analysis of Stability in Hamiltonian Flows | We study the stability and breakup of invariant tori in Hamiltonian flows
using a combination of Kolmogorov-Arnold-Moser (KAM) theory and
renormalization-group techniques. We implement the scheme numerically for a
family of Hamiltonians quadratic in the actions to analyze the strong coupling
regime. We show that the KA... | 9802021v1 |
1998-10-19 | Coupled Microwave Billiards as a Model for Symmetry Breaking | Two superconducting microwave billiards have been electromagnetically coupled
in a variable way. The spectrum of the entire system has been measured and the
spectral statistics analyzed as a function of the coupling strength. It is
shown that the results can be understood in terms of a random matrix model of
quantum me... | 9810024v1 |
1999-09-17 | Finite Wavelength Instabilities in a Slow Mode Coupled Complex Ginzburg-Landau Equation | In this letter, we discuss the effect of slow real modes in
reaction-diffusion systems close to a supercritical Hopf bifurcation. The
spatio-temporal effects of the slow mode cannot be captured by traditional
descriptions in terms of a single complex Ginzburg-Landau equation (CGLE). We
show that the slow mode coupling ... | 9909028v1 |
1992-08-15 | Dynamic Scaling of Coupled Nonequilibrium Interfaces | We propose a simple discrete model to study the nonequilibrium fluctuations
of two locally coupled 1+1 dimensional systems (interfaces). Measuring
numerically the tilt-dependent velocity we construct a set of stochastic
continuum equations describing the fluctuations in the model
The scaling predicted by the equation... | 9208010v1 |
1992-11-04 | Level repulsion in integrable and almost-integrable quantum spin models | The repartition of the separation between energy levels of various isotropic
S=1/2 antiferromagnetic chains is studied numerically with the aim of
investigating the transition from integrable to non-integrable systems. We
begin by displaying the level separation distribution of the integrable Bethe
chain. Then two non-... | 9211004v1 |
1993-02-12 | SU(N) Antiferromagnets and Strongly Coupled QED: Effective Field Theory for Josephson Junctions Arrays | We review our analysis of the strong coupling of compact QED on a lattice
with staggered Fermions. We show that, for infinite coupling, compact QED is
exactly mapped in a quantum antiferromagnet. We discuss some aspects of this
correspondence relevant for effective field theories of Josephson junctions
arrays. | 9302016v1 |
1994-02-23 | Period Doubling in Four-Dimensional Volume-Preserving Maps | We numerically study the scaling behavior of period doublings at the
zero-coupling critical point in a four-dimensional volume-preserving map
consisting of two coupled area-preserving maps. In order to see the fine
structure of period doublings, we extend the simple one-term scaling law to a
two-term scaling law. Thus ... | 9402099v1 |
1994-07-25 | Magnetic phase diagram of the Hubbard model | The competition between commensurate and incommensurate spin-density-wave
phases in the infinite-dimensional single-band Hubbard model is examined with
quantum Monte Carlo simulation and strong and weak coupling approximations.
Quantum fluctuations modify the weak-coupling phase diagram by factors of order
unity and pr... | 9407101v1 |
1994-08-05 | Strong Coupling Expansions for Antiferromagnetic Heisenberg S=1/2 Ladders | The properties of antiferromagnetic Heisenberg $S=\frac{1}{2}$ ladders with
2, 3, and 4 chains are expanded in the ratio of the intra- and interchain
coupling constants. A simple mapping procedure is introduced to relate the 4
and 2-chain ladders which holds down to moderate values of the expansion
parameters. A second... | 9408023v1 |
1994-10-28 | Interplane relaxation and the bilayer coupling in Y$_2$Ba$_4$Cu$_7$O$_{15}$ | The origin of the spin gap in the underdoped cuprate superconductors is still
mysterious. Experimental evidence from neutron scattering and NMR experiments
indicates that the spin gap might be present only in the bilayer compounds. A
naive calculation for a two plane Heisenberg model locates the order-disorder
transiti... | 9410108v1 |
1994-11-17 | Andreev Spectroscopy of Josephson Coupling | It is shown that the low energy spectrum of mesoscopic superconductors
coupled by Josephson interaction can be probed by two-electron tunneling from a
normal electrode. The Andreev reflection in the NS junction of a
normal-superconductor-superconductor double junction (NSS transistor) provides
a unique spectroscopic to... | 9411070v1 |
1994-11-30 | Coupled-Map Modeling of One-Dimensional Traffic Flow | We propose a new model of one-dimensional traffic flow using a coupled map
lattice. In the model, each vehicle is assigned a map and changes its velocity
according to it. A single map is designed so as to represent the motion of a
vehicle properly, and the maps are coupled to each other through the headway
distance. By... | 9411129v1 |
1994-12-15 | Magnetic Moment and Perturbation Theory with Singular Magnetic Fields | The spectrum of a charged particle coupled to Aharonov-Bohm/anyon gauge
fields displays a nonanalytic behavior in the coupling constant. Within
perturbation theory, this gives rise to certain singularities which can be
handled by adding a repulsive contact term to the Hamiltonian. We discuss the
case of smeared flux tu... | 9412078v1 |
1995-01-04 | Rigorous results on a first-order phase transition in antiferromagnetic spin-1/2 coupled chains | Some rigorous results are presented for a first-order quantum phase
transition between the dimerized state and Haldane-type state (i.e., a state
similar to the ground state of the one-dimensional spin-1 Heisenberg chain) in
the spin-1/2 coupled chains with nearest-neighbour and next-nearest-neighbour
Heisenberg interac... | 9501006v1 |
1995-03-09 | Weak Coupling Phase Diagram of the Two Chain Hubbard Model | We present a general method for determining the phase diagram of systems of a
finite number of one dimensional Hubbard--like systems coupled by
single--particle hopping with weak interactions. The technique is illustrated
by detailed calculations for the two--chain Hubbard model, providing the first
controlled results ... | 9503045v1 |
1995-07-20 | Mixed symmetry superconductivity in two-dimensional Fermi liquids | We consider a 2D isotropic Fermi liquid with attraction in both $s$ and $d$
channels and examine the possibility of a superconducting state with mixed $s$
and $d$ symmetry of the gap function. We show that both in the weak coupling
limit and at strong coupling, a mixed $s+id$ symmetry state is realized in a
certain ran... | 9507085v1 |
1995-08-21 | A Microscopic Model of Non-Reciprocal Optical Effects in Cr_2 O_3 | This manuscript deals with the question "How does light couple to an
antiferromagnetic order parameter"? For that we develop a microscopic model
that explains the non-reciprocal optical effects in centrosymmetric Cr_2 O_3.
It is shown that light can couple {\em directly} to the antiferromagnetic order
parameter. This c... | 9508082v1 |
1995-08-23 | Strong-coupling expansions for the pure and disordered bose Hubbard model | A strong-coupling expansion for the phase boundary of the (incompressible)
Mott insulator is presented for the bose Hubbard model. Both the pure case and
the disordered case are examined. Extrapolations of the series expansions
provide results that are as accurate as the Monte Carlo simulations and agree
with the exact... | 9508101v1 |
1995-09-27 | Oscillatory Thickness Dependence of Magnetic Moments and interface-induced Changes of the Exchange Coupling in Co/Cu and Co-Ni/Cu Multilayers | We perform first-principles calculations for the three multilayer systems
(100)-Co_1/Cu_n, -NiCo_2Ni/Cu_n and -Co_4/Cu_n, and find from a comparison x of
the results for system 2 and 3 that amplitude and phase of the exchange
coupling are sensitive to the magnetic-slab/nonmagnetic-spacer interface.
Moreover, we observe... | 9509164v1 |
1995-10-05 | On Synchronization in a Lattice Model of Pulse-Coupled Oscillators | We analyze the collective behavior of a lattice model of pulse-coupled
oscillators. By means of computer simulations we find the relation between the
intrinsic dynamics of each member of the population and their mutual
interaction that ensures, in a general context, the existence of a fully
synchronized regime. This co... | 9510029v1 |
1995-10-27 | Persistent currents in coupled mesoscopic rings | We have analysed the nature of persistent currents in open coupled mesoscopic
rings. Our system is comprised of two ideal loops connected to an electron
reservoir. We have obtained analytical expressions for the persistent current
densities in two rings in the presence of a magnetic field. We show that the
known even-o... | 9510158v1 |
1995-11-17 | The Isotope Effect in d-Wave Superconductors | Based on recently proposed anti-ferromagnetic spin fluctuation exchange
models for $d_{x^2-y^2}$-superconductors, we show that coupling to harmonic
phonons {\it{cannot}} account for the observed isotope effect in the cuprate
high-$T_c$ materials, whereas coupling to strongly anharmonic multiple-well
lattice tunneling m... | 9511086v1 |
1995-12-22 | Theory of Nuclear Magnetic Relaxation in Haldane Gap Materials: An Illustration of the Use of (1+1)-Dimensional Field Theory Techniques | A comprehensive theory of nuclear magnetic relaxation is developed for
Haldane Gap materials using nonlinear sigma, boson and fermion models. We
include a thorough discussion of of the effects of interchain couplings,
nearest neighbour hyperfine couplings and crystal structure. We also introduce
a new theory of impurit... | 9512161v2 |
1996-02-11 | Theory on the Itinerant Ferromagnetism in the $3d$-transition metal systems | Keeping nickel, cobalt and iron in mind, we investigate the origin of the
itinerant ferromagnetism. In so doing, we generalize the Gutzwiller
approximation. In that,we take account of the effect of the band degeneracy and
the Hund's-rule coupling in addition to the on-site repulsion. After the
discussion on nickel, the... | 9602058v1 |
1996-02-21 | Effect of randomness in many coupled Potts models | Using 2-loop renormalisation group calculations, we study a system of $N$
two-dimensional Potts models with random bonds coupled together by their local
energy density. This model can be seen as a generalization of the random
Ashkin-Teller model. We found that, depending on the sign of the coupling term,
the universali... | 9602116v1 |
1996-04-23 | Dynamics of coupled quantum spin chains | Static and dynamical properties of weakly coupled antiferromagnetic spin
chains are treated using a mean--field approximation for the interchain
coupling and exact results for the resulting effective one--dimensional
problem. Results for staggered magnetization, N\'eel temperature and spin wave
excitations are in agree... | 9604144v2 |
1996-06-07 | Analytic Bethe Ansatz for 1-D Hubbard model and twisted coupled XY model | We found the eigenvalues of the transfer matrices for the 1-D Hubbard model
and for the coupled XY model with twisted boundary condition by using the
analytic Bethe Ansatz method. Under a particular condition the two models have
the same Bethe Ansatz equations. We have also proved that the periodic 1-D
Hubbard model is... | 9606039v1 |
1996-06-23 | Coulomb effects in artificial molecules | We study the capacitance spectra of artificial molecules consisting of two
and three coupled quantum dots from an extended Hubbard Hamiltonian model that
takes into account quantum confinement, intra- and inter-dot Coulomb
interaction and tunneling coupling between all single particle states in
nearest neighbor dots. W... | 9606163v1 |
1996-06-27 | Nature of eigenstates in a mesoscopic ring coupled to a side branch | We formalize the parity effect of a multichannel ring coupled to a side
branch using the tight binding model. We find that the tight binding model
gives slightly different result from the continuum model. We also show that
some states of the system can be nonmagnetic. In the multichannel ring coupled
to a side branch, ... | 9606202v1 |
1996-07-29 | Intermediate-Coupling Theory for the Spectral Weight of Spin Polaron | Within the intermediate-coupling theory, the quasiparticle weight $Z$ of one
hole injected in the undoped antiferromagnetic ground state is studied. We find
that, for the hole located at the quasiparticle band minimun with momentum
${\bf k}_0 = (\pm \frac{\pi}{2}, \pm \frac{\pi}{2})$, $Z$ is finite. By
comparing the re... | 9607204v1 |
1996-11-07 | Aging and effective temperatures in the low temperature mode-coupling equations | The low-temperature generalization of the mode-coupling equations corresponds
to the dynamics of mean-field disordered models in the glassy phase. The system
never achieves equilibrium, preserving the memory of the time elapsed after the
quench throughout its evolution. A concept of effective temperature can be made
qu... | 9611051v1 |
1996-11-26 | Nonlinear Transport through Coupled Double Quantum Dot Systems | We investigate sequential tunneling transport through a semiconductor double
quantum dot structure by combining a simple microscopic quantum confinement
model with a Mott-Hubbard type correlation model. We calculate
nonperturbatively the evolution of the Coulomb blockade oscillations as a
function of the interdot barri... | 9611200v1 |
1997-03-25 | Phase Diagram of the S = 1/2 Frustrated Coupled Ladder System | We present a theoretical study of the magnetic phase diagram of the
frustrated coupled ladder structure realized recently in several materials.
This system displays a nondegenerate spin-gap state in the dimer limit and an
infinitely degenerate spin-gap state in the regime of weakly-coupled zig-zag
chains. Between these... | 9703214v1 |
1997-04-01 | Interacting electrons on a half line coupled to impurities | We generalize the bosonization methods for systems in the half line that we
discussed elsewhere, to study the effects of interactions on electronic systems
coupled to impurities. We introduce a model for a quantum wire coupled with a
quantum dot by a purely capacitive interaction. We show that the effect on the
quantum... | 9704012v1 |
1997-05-23 | Sonoluminescence: Coupling to an Applied Magnetic Field | We investigate several means of coupling between a sonoluminescing bubble and
an applied magnetic field. Recent experiments show a strong quadratic
dependence between the forcing pressures required for stable sonoluminescence
and magnetic field amplitude. However, all coupling mechanisms calculated here
for comparable ... | 9705239v3 |
1997-07-23 | Critical Behavior of Coupled q-state Potts Models under Weak Disorder | We investigate the effect of weak disorder on different coupled $q$-state
Potts models with $q\le 4$ using two loops renormalisation group. This study
presents new examples of first order transitions driven by randomness. We found
that weak disorder makes the models decouple. Therefore, it appears that no
relations eme... | 9707238v1 |
1997-08-15 | Charge Fluctuations in a Quantum Dot with a Dissipative Environment | We consider a multiple tunneling process into a quantum dot capacitively
coupled to a dissipative environment. The problem is mapped onto an anisotropic
Kondo model in its Coulomb gas representation. The tunneling barrier resistance
and the dissipative resistance of the environment correspond to the transverse
and the ... | 9708109v1 |
1997-09-29 | Superconductivity, Josephson coupling and order parameter symmetry in striped cuprates | We consider a renormalization group study of the problem of coupled stripes
of holes in cuprates. We use a model of a mesh of horizontal and vertical
stripes and study the problemof superconductivity via the Josephson coupling.
We discuss the evolution of the Fermi surface with doping and temperature, the
existence of ... | 9709324v2 |
1997-10-13 | The gap maximum of anisotropic superconductors | For a completely general anisotropic order parameter (including changes of
sign), we show that weak coupling theory is incompatible with high values of
the maximum \Delta_{M} of the zero temperature gap as compared to the critical
temperature T_{c}, such as those found experimentally in
Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}... | 9710115v1 |
1997-10-24 | Infinite coupling magnon theory of quantum Heisenberg magnetic models of spin s | An infinity magnon coupling term is introduced into the Holstein-Primakoff
transformed forms of the Heisenberg ferromagnetic and antiferromagnetic models
of any spin $s$ to rigorously remove the unphysical magnon states. This term
makes the series expansion of the square root of the magnon operators become a
finite ser... | 9710261v1 |
1997-11-11 | A New Quantum Phase Transition in the Coupled Quantum Dots System | We study two quantum dots in the limit of strong dot-lead coupling and weak
dot-dot tunneling. The model maps on Ising-coupled Kondo impurities. We argue
that a new quantum critical fixed point exists at an intermediate value of the
mutual capacitance, supporting non-Fermi liquid behaviour. We construct the
total condu... | 9711098v1 |
1997-12-17 | Mechanisms of synchronization and pattern formation in a lattice of pulse-coupled oscillators | We analyze the physical mechanisms leading either to synchronization or to
the formation of spatio-temporal patterns in a lattice model of pulse-coupled
oscillators. In order to make the system tractable from a mathematical point of
view we study a one-dimensional ring with unidirectional coupling. In such a
situation,... | 9712200v1 |
1998-01-14 | Pinning-induced transition to disordered vortex phase in layered superconductors | Destruction of the vortex lattice by random point pinning is considered as a
mechanism of the ``second peak'' transition observed experimentally in weakly
coupled layered high temperature superconductors. The transition field
separating the topologically ordered quasilattice from the amorphous vortex
configuration is s... | 9801144v1 |
1998-02-04 | Dynamical effects of phonons on soliton binding in spin-Peierls systems | The role of dynamical magneto-elastic coupling in spin-Peierls chains is
investigated by numerical and analytical techniques. We show that a Heisenberg
spin chain coupled to dynamical optical phonons exhibits a transition towards a
spontaneously dimerized state in a wide range of parameter space. The low
energy excitat... | 9802053v2 |
1998-02-11 | Nonequilibrium transport for crossed Luttinger liquids | Transport through two one-dimensional interacting metals (Luttinger liquids)
coupled together at a single point is analyzed. The dominant coupling mechanism
is shown to be of electrostatic nature. Describing the voltage sources by
boundary conditions then allows for the full solution of the transport problem.
For weak ... | 9802116v1 |
1998-03-14 | Microscopic conditions favoring itinerant ferromagnetism: Hund's rule coupling and orbital degeneracy | The importance of Hund's rule coupling for the stabilization of itinerant
ferromagnetism is investigated within a two-band Hubbard model. The magnetic
phase diagram is calculated by finite-temperature quantum Monte Carlo
simulations within the dynamical mean-field theory. Ferromagnetism is found in
a broad range of ele... | 9803182v2 |
1998-05-28 | Soliton Approach to Spin-Peierls Antiferromagnets: Large-Scale Numerical Results | A simple intuitive picture of spin-Peierls antiferromagnets arises from
regarding the elementary excitations as S=1/2 solitons. In a strictly
one-dimensional system these excitations are assumed not to form bound-states
and to be repelled by impurities. Couplings to the three-dimensional lattice
are assumed to produce ... | 9805386v1 |
1998-06-03 | Noise reduction in signal processing using binary couplings | We report a simple extension of a model for noise reduction in signal
processing, already introduced by Mourik et al., in the presence of binary
coupling vectors, which turns to be more useful for practical and engineering
implementations. We also compute annealed approximation which gives an upper
bound of the correct... | 9806037v1 |
1998-06-15 | Mean field theory of critical coupled map lattices | We study the single-site approximation of the Perron-Frobenius equation for a
coupled map lattice exhibiting a phase transition at a critical value g_c of
the coupling constant. We found that the critical exponents are the same as in
the usual mean-field theory of equilibrium statistical mechanics. Remarkably,
the valu... | 9806177v1 |
1998-07-13 | Exponential behavior of the interlayer exchange coupling across non-magnetic metallic superlattices | It is shown that the coupling between magnetic layers separated by
non-magnetic metallic superlattices can decay exponentially as a function of
the spacer thickness $N$, as opposed to the usual $N^{-2}$ decay. This effect
is due to the lack of constructive contributions to the coupling from extended
states across the s... | 9807182v1 |
1998-07-16 | Level statistics of quantum dots coupled to reservoirs | We study the effect of electron tunneling on the level statistics of quantum
dots. While the coupling between individual levels and the electron reservoir
leads predominantly to the expected level broadening, the indirect coupling of
adjacent levels via the reservoir results in a new asymptotic level statistics
and bro... | 9807238v1 |
1998-08-18 | Synchronization of Coupled Systems with Spatiotemporal Chaos | We argue that the synchronization transition of stochastically coupled
cellular automata, discovered recently by L.G. Morelli {\it et al.} (Phys. Rev.
{\bf 58 E}, R8 (1998)), is generically in the directed percolation universality
class. In particular, this holds numerically for the specific example studied
by these au... | 9808199v1 |
1998-08-21 | Chiral Solitons in a Current Coupled Schrödinger Equation With Self Interaction | Recently non-topological chiral soliton solutions were obtained in a
derivatively coupled non-linear Schr\"odinger model in 1+1 dimensions. We
extend the analysis to include a more general self-coupling potential (which
includes the previous cases) and find chiral soliton solutions. Interestingly
even the magnitude of ... | 9808239v1 |
1998-09-10 | Quantum Phase Transitions in Capacitively Coupled Two-Dimensional Josephson-Junction Arrays | Quantum-phase transitions in two layers of ultrasmall Josephson junctions,
coupled capacitively with each other, are investigated. As the interlayer
capacitance is increased, the system at zero temperature is found to exhibit an
insulator-to-superconductor transition. It is shown that, unlike
one-dimensional arrays wit... | 9809157v1 |
1998-09-11 | N-tree approximation for the largest Lyapunov exponent of a coupled-map lattice | The N-tree approximation scheme, introduced in the context of random directed
polymers, is here applied to the computation of the maximum Lyapunov exponent
in a coupled map lattice. We discuss both an exact implementation for small
tree-depth $n$ and a numerical implementation for larger $n$s. We find that the
phase-tr... | 9809177v1 |
1998-09-18 | Array-induced collective transport in the Brownian motion of coupled nonlinear oscillator systems | Brownian motion of an array of harmonically coupled particles subject to a
periodic substrate potential and driven by an external bias is investigated. In
the linear response limit (small bias), the coupling between particles may
enhance the diffusion process, depending on the competition between the
harmonic chain and... | 9809247v1 |
1998-09-25 | Early time behavior of the order parameter coupled to a conserved density: A study in a semi-infinite geometry | We study the short time behavior of the order parameter coupled to a
conserved field in semi-infinite geometry. The short time exponent, obtained by
solving the one loop differential equations for the conserved density and the
order parameter, agrees with the prediction from a scaling argument based on
short distance e... | 9809354v1 |
1998-09-29 | Point contact spectroscopy and temperature dependence of resistivity of metallic sodium tungsten bronzes -Role of optical phonons | In this paper we report the results of electrical resistivity (1.5K < T
<300K) and point contact spectroscopy (PCS) measurements on single crystals of
metallic sodium tungsten bronze with varying sodium content. We have shown that
the electron-phonon coupling function as measured through PCS can explain
quantitatively ... | 9809393v1 |
1998-11-12 | Strong coupling resistivity in the Kondo model | By applying methods of integrable quantum field theory to the Kondo problem,
we develop a systematic perturbation expansion near the IR (strong coupling)
fixed point. This requires the knowledge of an infinity of irrelevant operators
and their couplings, which we all determine exactly. A low temperature
expansion (ie a... | 9811172v1 |
1998-11-19 | Metastable states and information propagation in a 1D array of locally-coupled bistable cells | We study the effect of metastable states on the relaxation process (and hence
information propagation) in locally coupled and boundary-driven structures. We
first give a general argument to show that metastable states are inevitable
even in the simplest of structures, a wire. At finite temperatures, the
relaxation mech... | 9811294v1 |
1998-11-29 | On the 'Strong-Coupling' Generalization of the Bogoliubov Model | A generalized Bogoliubov model of the Bose gas in the ground state is
proposed which properly takes into account both the long-range and short-range
spatial boson correlations. It concerns equilibrium characteristics and
operates with in-medium Schrodinger equations for the pair wave functions of
bosons being the eigen... | 9811405v2 |
1998-12-24 | The Charge Ordered State from Weak to Strong Coupling | We apply the Dynamical Mean Field Theory to the problem of charge ordering.
In the normal state as well as in the Charge Ordered (CO) state the existence
of polarons, i.e. electrons strongly coupled to local lattice deformation, is
associated to the qualitative properties of the Lattice Polarization
Distribution Functi... | 9812393v1 |
1999-01-19 | On Coupled Directed Percolation Processes: A Unifying View | It is shown that the universal critical properties of two recently introduced
coupled directed percolation processes can be described by a single rapidity
reversal invariant stochastic reaction-diffusion model. It is demonstrated that
all renormalizations needed for the calculation of the universal scaling
behavior nea... | 9901188v1 |
1999-02-09 | Many-chain Generalization of Gauge-Coupled Fermionic Systems | We present a many chain generalization of a recent work of ours, wherein an
arbitrary number of fermionic chains are coupled via a Gauge interaction.
Central to this construction is the role of an antisymmetric tensor which
enters the couplings and helps define a pseudo-unitary transformation, that
maps the models on t... | 9902114v1 |
1999-02-09 | Mode Spectroscopy and Level Coupling in Ballistic Electron Waveguides | A tunable quantum point contact with modes occupied in both transverse
directions is studied by magnetotransport experiments. We use conductance
quantization of the one-dimensional subbands as a tool to determine the mode
spectrum. A magnetic field applied along the direction of the current flow
couples the modes. This... | 9902119v1 |
1999-02-18 | Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7 | Inelastic neutron-scattering measurements were performed on a single crystal
of the layered colossal magnetoresistance (CMR) material La1.2Sr1.8Mn2O7 (Tc ~
120K). We found that the spin wave dispersion is almost perfectly
two-dimensional with the in-plane spin stiffness constant D ~ 151meVA. The
value is similar to tha... | 9902253v1 |
1999-03-01 | Phase Ordering and Onset of Collective Behavior in Chaotic Coupled Map Lattices | The phase ordering properties of lattices of band-chaotic maps coupled
diffusively with some coupling strength $g$ are studied in order to determine
the limit value $g_e$ beyond which multistability disappears and non-trivial
collective behavior is observed. The persistence of equivalent discrete spin
variables and the... | 9903018v1 |
1999-03-08 | Confinement-deconfinement transition in two-coupled chains with umklapp scattering | A role of umklapp scattering has been examined for two-coupled chains with
both forward and backward scatterings by applying renormalization group method
to bosonized Hamiltonian. It has been found that a state with relevant
interchain hopping changes into a state with irrelevant (confined) one when the
magnitude of um... | 9903135v1 |
1999-03-20 | Comparison of superconductivity in Sr_2RuO_4 and copper oxides | To compare the superconductivity in strongly correlated electron systems with
the antiferromagnetic fluctuations in the copper oxides and with the
ferromagnetic fluctuations in Sr_2RuO_4 a t-J-I model is proposed. The
antiferromagnetic coupling J results in the superconducting state of
d_{x^2-y^2} symmetry and the ferr... | 9903314v1 |
1999-04-01 | Exact phase diagrams for an Ising model on a two-layer Bethe lattice | Using an iteration technique, we obtain exact expressions for the free energy
and the magnetization of an Ising model on a two - layer Bethe lattice with
intralayer coupling constants J1 and J2 for the first and the second layer,
respectively, and interlayer coupling constant J3 between the two layers; the
Ising spins ... | 9904008v1 |
1999-04-07 | Perpendicular transport and magnetization processes in magnetic multilayers with strongly and weakly coupled magnetic layers | Within the framework of a two-band tight-binding model, we have performed
calculations of giant magnetoresistance, exchange coupling and thermoelectric
power (TEP) for a system consisting of three magnetic layers separated by two
non-magnetic spacers with the first two magnetic layers strongly
antiferromagnetically exc... | 9904086v1 |
1999-04-28 | Model Calculation of Electron-Phonon Couplings in a Dimer with a Non-Degenerate Orbital | We evaluate all the electron-phonon couplings derived from the one-body
electronic interactions, in both the adiabatic and extreme non-adiabatic limit,
for a dimer with a non-degenerate orbital built from atomic wave functions of
Gaussian shape. We find largely different values of the coupling parameters in
the two cas... | 9904405v2 |
1999-04-30 | Does spin-orbit coupling play a role in metal-nonmetal transition in two-dimensional systems? | We propose an experiment, which would allow to pinpoint the role of
spin-orbit coupling in the metal-nonmetal transition observed in a number of
two-dimensional systems at low densities. Namely, we demonstrate that in a
parallel magnetic field the interplay between the spin-orbit coupling and the
Zeeman splitting leads... | 9904451v2 |
1999-05-11 | Critical renormalized coupling constants in the symmetric phase of the Ising models | Using a novel finite size scaling Monte Carlo method, we calculate the four,
six and eight point renormalized coupling constants defined at zero momentum in
the symmetric phase of the three dimensional Ising system. The results of the
2D Ising system that were directly measured are also reported. Our values of
the six ... | 9905138v1 |
1999-05-11 | Ballistic Four-Terminal Josephson Junction: Bistable States and Magnetic Flux Transfer | The macroscopic quantum interference effects in ballistic Josephson
microstructures are investigated. The studied system consists of four bulk
superconductors (terminals) which are weakly coupled through the mesoscopic
rectangular normal metal (two dimensional electron gas). We show that nonlocal
electrodynamics of bal... | 9905139v1 |
1999-05-14 | Scaling and finte-size-scaling in the two dimensional random-coupling Ising ferromagnet | It is shown by Monte Carlo method that the finite size scaling (FSS) holds in
the two dimensional random-coupled Ising ferromagnet. It is also demonstrated
that the form of universal FSS function constructed via novel FSS scheme
depends on the strength of the random coupling for strongly disordered cases.
Monte Carlo m... | 9905202v1 |
1999-05-15 | Critical Behavior of Anisotropic Heisenberg Mixed-Spin Chains in a Field | We numerically investigate the critical behavior of the spin-(1,1/2)
Heisenberg ferrimagnet with anisotropic exchange coupling in a magnetic field.
A quantized magnetization plateau as a function of the field, appearing at a
third of the saturated magnetization, is stable over whole the
antiferromagnetic coupling regio... | 9905224v1 |
1999-06-01 | Two-dimensional behavior of the sublattice magnetization in three-dimensional Ising antiferromagnets | A three-dimensional layered Ising-Antiferromagnet with a ferromagnetic
intra-layer coupling to z neighbors, zJ > 0, and an antiferromagnetic
interlayer coupling to z' neighbors, z'J' < 0, is investigated by Monte Carlo
simulations on a hexagonal lattice. The physical nature of the anomalous
temperature bahavior of the ... | 9906003v1 |
1999-06-21 | Comment on "Intermittent Synchronization in a Pair of Coupled Chaotic Pendula" | In [G. Baker et al., Phys. Rev. Lett. 81, 554 (1998)] a number of supposedly
novel and surprising features were observed in a system composed of two
periodically driven and asymmetrically coupled pendula. In particular it was
claimed that `permanent synchronization ... does not occur except as a
numerical artifact'. It... | 9906312v1 |
1999-06-29 | Pattern selection in a lattice of pulse-coupled oscillators | We study spatio-temporal pattern formation in a ring of N oscillators with
inhibitory unidirectional pulselike interactions. The attractors of the
dynamics are limit cycles where each oscillator fires once and only once. Since
some of these limit cycles lead to the same pattern, we introduce the concept
of pattern dege... | 9906436v1 |
1999-07-13 | Self-similar magnetoresistance of Fibonacci ultrathin magnetic films | We study numerically the magnetic properties (magnetization and
magnetoresistance) of ultra-thin magnetic films (Fe/Cr) grown following the
Fibonacci sequence. We use a phenomenological model which includes Zeeman,
cubic anisotropy, bilinear and biquadratic exchange energies. Our physical
parameters are based on experi... | 9907200v1 |
1999-07-30 | Synchronization and resonance in a driven system of coupled oscillators | We study the noise effects in a driven system of globally coupled
oscillators, with particular attention to the interplay between driving and
noise. The self-consistency equation for the order parameter, which measures
the collective synchronization of the system, is derived; it is found that the
total order parameter ... | 9907477v1 |
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