993 research outputs found
Magnetization distribution in the transverse Ising chain with energy flux
The zero-temperature transverse Ising chain carrying an energy flux j_E is
studied with the aim of determining the nonequilibrium distribution functions,
P(M_z) and P(M_x), of its transverse and longitudinal magnetizations,
respectively. An exact calculation reveals that P(M_z) is a Gaussian both at
j_E=0 and j_E not equal 0, and the width of the distribution decreases with
increasing energy flux. The distribution of the order-parameter fluctuations,
P(M_x), is evaluated numerically for spin-chains of up to 20 spins. For the
equilibrium case (j_E=0), we find the expected Gaussian fluctuations away from
the critical point while the critical order-parameter fluctuations are shown to
be non-gaussian with a scaling function Phi(x)=Phi(M_x/)=P(M_x)
strongly dependent on the boundary conditions. When j_E not equal 0, the system
displays long-range, oscillating correlations but P(M_x) is a Gaussian
nevertheless, and the width of the Gaussian decreases with increasing j_E. In
particular, we find that, at critical transverse field, the width has a
j_E^(-3/8) asymptotic in the j_E -> 0 limit.Comment: 8 pages, 5 ps figure
Quantum shock waves in the Heisenberg XY model
We show the existence of quantum states of the Heisenberg XY chain which
closely follow the motion of the corresponding semi-classical ones, and whose
evolution resemble the propagation of a shock wave in a fluid. These states are
exact solutions of the Schroedinger equation of the XY model and their
classical counterpart are simply domain walls or soliton-like solutions.Comment: 15 pages,6 figure
Steady-state selection in driven diffusive systems with open boundaries
We investigate the stationary states of one-dimensional driven diffusive
systems, coupled to boundary reservoirs with fixed particle densities. We argue
that the generic phase diagram is governed by an extremal principle for the
macroscopic current irrespective of the local dynamics. In particular, we
predict a minimal current phase for systems with local minimum in the
current--density relation. This phase is explained by a dynamical phenomenon,
the branching and coalescence of shocks, Monte-Carlo simulations confirm the
theoretical scenario.Comment: 6 pages, 5 figure
The Diffusion of the Magnetization Profile in the XX-model
By the -algebraic method, we investigate the magnetization profile in
the intermediate time of diffusion. We observe a transition from monotone
profile to non-monotone profile. This transition is purely thermal.Comment: Accepted for publication in Phys. Rev.
Comparing electricity transitions:
AbstractThis paper contributes to understanding national variations in using low-carbon electricity sources by comparing the evolution of nuclear, wind and solar power in Germany and Japan. It develops and applies a framework for analyzing low-carbon electricity transitions based on interplay of techno-economic, political and socio-technical processes. We explain why in the 1970s–1980s, the energy paths of the two countries were remarkably similar, but since the 1990s Germany has become a leader in renewables while phasing out nuclear energy, whereas Japan has deployed less renewables while becoming a leader in nuclear power. We link these differences to the faster growth of electricity demand and energy insecurity in Japan, the easier diffusion of onshore wind power technology and the weakening of the nuclear power regime induced by stagnation and competition from coal and renewables in Germany. We show how these changes involve the interplay of five distinct mechanisms which may also play a role in other energy transitions
Probability distribution of magnetization in the one-dimensional Ising model: Effects of boundary conditions
Finite-size scaling functions are investigated both for the mean-square
magnetization fluctuations and for the probability distribution of the
magnetization in the one-dimensional Ising model. The scaling functions are
evaluated in the limit of the temperature going to zero (T -> 0), the size of
the system going to infinity (N -> oo) while N[1-tanh(J/k_BT)] is kept finite
(J being the nearest neighbor coupling). Exact calculations using various
boundary conditions (periodic, antiperiodic, free, block) demonstrate
explicitly how the scaling functions depend on the boundary conditions. We also
show that the block (small part of a large system) magnetization distribution
results are identical to those obtained for free boundary conditions.Comment: 8 pages, 5 figure
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