Sudden and Slow Quenches into the Antiferromagnetic Phase of Ultracold Fermions

AbstractWe propose a method to reach the antiferromagnetic state of two-dimensional Fermi gases trapped in optical lattices: Independent subsystems are prepared in suitable initial states and then connected by a sudden or slow quench of the tunneling between the subsystems. Examples of suitable low-entropy subsystems are double wells or plaquettes, which can be experimentally realised in Mott insulating shells using optical super-lattices. We estimate the effective temperature T* of the system after the quench by calculating the distribution of excitations created using the spin wave approximation in a Heisenberg model. We investigate the effect of an initial staggered magnetic field and find that for an optimal polarisation of the initial state the effective temperature can be significantly reduced from T*≈1.7 Tc at zero polarisation to T*<0.65Tc, where Tc is the crossover temperature to the antiferromagnetic state. The temperature can be further reduced using a finite quench time. We also show that T* decreases logarithmically with the linear size of the subsystem.

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Non-Equilibrium Critical Relaxation of Heisenberg Ferromagnets with Long-Range Correlated Defects

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.190.39 ◽

2012 ◽

Vol 190 ◽

pp. 39-42

Author(s):

M. Medvedeva ◽

Pavel V. Prudnikov

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Critical Behavior ◽

Critical Exponents ◽

Heisenberg Model ◽

Three Dimensional ◽

Initial State ◽

Short Time ◽

Theoretic Description ◽

Good Agreement

The dynamic critical behavior of the three-dimensional Heisenberg model with longrangecorrelated disorder was studied by using short-time Monte Carlo simulations at criticality.The static and dynamic critical exponents are determined. The simulation was performed fromordered initial state. The obtained values of the exponents are in a good agreement with resultsof the field-theoretic description of the critical behavior of this model in the two-loopapproximation.

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ENTROPIC ISSUES IN CONTEMPORARY COSMOLOGY

International Journal of Modern Physics D ◽

10.1142/s0218271803003530 ◽

2003 ◽

Vol 12 (06) ◽

pp. 963-976 ◽

Cited By ~ 3

Author(s):

D. H. COULE

Keyword(s):

Degrees Of Freedom ◽

Second Law Of Thermodynamics ◽

High Energy ◽

Big Bang ◽

Accelerating Universe ◽

De Sitter ◽

Initial State ◽

Start Time ◽

Acceleration Of The Universe ◽

Low Entropy

Penrose1 has emphasized how the initial big bang singularity requires a special low entropy state. We address how recent brane cosmological schemes address this problem and whether they offer any apparent resolution. Pushing the start time back to t = -∞, or utilizing maximally symmetric AdS spaces, simply exacerbates or transfers the problem. Since the entropy of de Sitter space is S ≤ 1/Λ, using the present acceleration of the universe as a low energy (Λ ~ 10-120) inflationary stage, as in cyclic ekpyrotic models, produces a gravitational heat death after one cycle. Only higher energy driven inflation, together with a suitable, quantum gravity holography style, restriction on ab initio degrees of freedom, gives a suitable low entropy initial state. We question the suggestion that a high energy inflationary stage could be naturally reentered by Poincaré recurrence within a finite causal region of an accelerating universe. We further give a heuristic argument that the so-called eternal inflation is not consistent with the second law of thermodynamics within a causal patch.

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Magnon Excitation Spectrum in Ferromagnetic Quasicubic Manganites

IEEE Transactions on Magnetics ◽

10.1109/tmag.2010.2044371 ◽

2010 ◽

Vol 46 (6) ◽

pp. 1295-1298 ◽

Cited By ~ 1

Author(s):

P. Schlottmann

Keyword(s):

Excitation Spectrum ◽

Spin Wave ◽

Heisenberg Model ◽

Double Exchange ◽

Zone Boundary ◽

Wave Approximation ◽

Hund’S Rule ◽

Jahn Teller ◽

Hund's Rule ◽

Magnon Excitation

The magnon excitation spectrum of ferromagnetic quasicubic manganites is studied by using the linearized spin-wave approximation for the double-exchange and the superexchange interactions. Two situations are distinguished: 1) a rigid coupling of the t2gand egspins via a large Hund's rule coupling and 2) a softened coupling between these spins (e.g., due to coupling of the egelectrons to Jahn-Teller modes). Case 2) leads to a softening of the magnon dispersion (compared to the Heisenberg model) close to the zone boundary.

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ANTIFERROMAGNETISM AND HOLE CONCENTRATION IN THE LINEAR SPIN WAVE APPROXIMATION OF THE t-J MODEL

Modern Physics Letters B ◽

10.1142/s0217984994000133 ◽

1994 ◽

Vol 08 (02) ◽

pp. 131-136 ◽

Cited By ~ 2

Author(s):

A. BELKASRI ◽

J.L. RICHARD

Keyword(s):

Spin Wave ◽

Order Parameter ◽

Degrees Of Freedom ◽

Hole Concentration ◽

Mean Field ◽

Field Approximation ◽

Mean Field Approximation ◽

Antiferromagnetic State ◽

Wave Approximation ◽

The Mean

The interplay between antiferromagnetic state and low doping regime is studied within the framework of the t-J model. The staggered magnetization is calculated in the mean field approximation by separating spin and charge degrees of freedom. We have obtained that this order parameter decreases with increasing doping and vanishes for some critical hole concentration.

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ON THE ORIGIN OF TIME AND THE UNIVERSE

International Journal of Modern Physics A ◽

10.1142/s0217751x10049013 ◽

2010 ◽

Vol 25 (12) ◽

pp. 2515-2523 ◽

Cited By ~ 8

Author(s):

VISHNU JEJJALA ◽

MICHAEL KAVIC ◽

DJORDJE MINIC ◽

CHIA-HSIUNG TZE

Keyword(s):

Matrix Theory ◽

Geodesic Distance ◽

Big Bang ◽

Arrow Of Time ◽

Initial State ◽

Infinite Dimensional ◽

Zero Entropy ◽

The Big Bang ◽

Low Entropy ◽

The Universe

We present a novel solution to the low entropy and arrow of time puzzles of the initial state of the universe. Our approach derives from the physics of a specific generalization of Matrix theory put forth in earlier work as the basis for a quantum theory of gravity. The particular dynamical state space of this theory, the infinite-dimensional analogue of the Fubini–Study metric over a complex nonlinear Grassmannian, has recently been studied by Michor and Mumford. The geodesic distance between any two points on this space is zero. Here we show that this mathematical result translates to a description of a hot, zero entropy state and an arrow of time after the Big Bang. This is modeled as a far from equilibrium, large fluctuation driven, "freezing by heating" metastable ordered phase transition of a nonlinear dissipative dynamical system.

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Enhanced cooling of micromechanical oscillator in the atom-assisted optomechanical cavity

International Journal of Quantum Information ◽

10.1142/s0219749914500051 ◽

2014 ◽

Vol 12 (01) ◽

pp. 1450005 ◽

Cited By ~ 3

Author(s):

Yan Han ◽

Wen-Zhao Zhang ◽

Jiong Cheng ◽

Ling Zhou

Keyword(s):

Radiation Pressure ◽

Effective Temperature ◽

Mechanical Oscillator ◽

Initial State ◽

Atomic Medium ◽

Optomechanical Cavity

We investigate the two-mode optomechanical cavity coupled with the three-level cascade atom. We propose a scheme to enhance the cooling of optomechanical oscillator by introducing atomic medium. Our results show that the existence of the atom can lead to a lower effective temperature of mechanical oscillator comparing to the case without atom. The coherence of the injected atomic affects the population of the photon, which can lead to the change in the radiation pressure on the movable mirror. We also show that the cooling of the mechanical oscillator is affected by initial state of inserting atom.

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Memory, the fork asymmetry, and the initial state

Synthese ◽

10.1007/s11229-021-03214-4 ◽

2021 ◽

Author(s):

Athamos Stradis

Keyword(s):

Probability Distribution ◽

Explanatory Gap ◽

Initial State ◽

The Past ◽

The Future ◽

Past Hypothesis ◽

Initial Probability Distribution ◽

Low Entropy

AbstractWhy do we have records of the past and not the future? Entropic explanations for this ‘record asymmetry’ have been popular ever since Boltzmann. Foremost amongst these is Albert and Loewer’s account, which explains the record asymmetry using a low-entropy initial macrostate (the ‘Past Hypothesis’) plus an initial probability distribution. However, the details of how this initial state underpins the record asymmetry are not fully specified. In this paper I attempt to plug this explanatory gap in two steps. First, I suggest the record asymmetry is more immediately explained by the ‘fork asymmetry’, which their picture omits. Second, by relating the fork asymmetry to an initial state that’s metaphysically similar to theirs, I clarify how this ultimately underpins the record asymmetry.

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Is the hypothesis about a low entropy initial state of the Universe necessary for explaining the arrow of time?

Physical Review D ◽

10.1103/physrevd.94.023520 ◽

2016 ◽

Vol 94 (2) ◽

Cited By ~ 4

Author(s):

Sheldon Goldstein ◽

Roderich Tumulka ◽

Nino Zanghì

Keyword(s):

Arrow Of Time ◽

Initial State ◽

Low Entropy ◽

The Universe

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THE ENTROPY GAP AND THE TIME ASYMMETRY

Modern Physics Letters A ◽

10.1142/s021773239600076x ◽

1996 ◽

Vol 11 (09) ◽

pp. 755-762 ◽

Cited By ~ 6

Author(s):

ROBERTO AQUILANO ◽

MARIO CASTAGNINO

Keyword(s):

Observational Data ◽

Homogeneous Model ◽

Initial State ◽

Time Asymmetry ◽

Universe Expansion ◽

Low Entropy ◽

The Universe

The universe time asymmetry is essentially produced by its low-entropy unstable initial state. Using quantitative arguments P. Davies2 has demonstrated that the universe expansion may produce a decreasing of entropy and, therefore, this fact explains its low-entropy states. This idea is implemented in a qualitative way in a simple homogeneous model. A rough coincidence with observational data is found.

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