1,655 research outputs found
Thermally stable multipartite entanglements in the frustrated Heisenberg hexagon
Thermally stable quantum states with multipartite entanglements led by
frustration are found in the antiferromagnetic spin-1/2 Heisenberg hexagon. The
model has been solved exactly to obtain all analytic expressions of eigenvalues
and eigenfunctions. Detection and characterizations for various types of
entanglements have been carried out in terms of concurrence and entanglement
witnesses based on several thermodynamic observables. Variations of
entanglement properties with respect to temperature and frustration are
discussed. Even though the frustration opposes the bipartite entanglement, it
favors the multipartite entanglement. Entangled states exhibit robustness
against the thermal effects in the presence of frustration and they are found
to survive at any temperature.Comment: 25 pages, double space, single column, 5 figure
Thai financial sector efficiency prior to the East Asian financial crisis
This paper looks at whether differences in the form of ownership were not the cause of the productivity differences but that these differences were due to individual firm effects. We also want to examine the belief that inefficiency in the Thai financial sector was not one of the causal factors in the currency crisis in 1997 with a high level of overall efficiency and some firms outperforming this norm. A regression of total revenue on capital, labour, company dummies and time dummies reveals that the average growth rate of total revenue allowing for changes in labour and capital and inter-firm efficiency differences was 3.6% for the period 1989 to 1996. The same regression also provides evidence that in the Thai insurance sector, larger companies are more efficient. However, no such similar evidence exists for the Thai banking sector.Thailand financial services efficiency
Noise-induced transition in a quantum system
We examine the noise-induced transition in a fluctuating bistable potential
of a driven quantum system in thermal equilibrium. Making use of a Wigner
canonical thermal distribution for description of the statistical properties of
the thermal bath, we explore the generic effects of quantization like vacuum
field fluctuation and tunneling in the characteristic stationary probability
distribution functions undergoing transition from unimodal to bimodal nature
and in signal-to-noise ratio characterizing the co-operative effect among the
noise processes and the weak periodic signal.Comment: To appear on Physics Letters
Noise-induced quantum transport
We analyze the problem of directed quantum transport induced by external
exponentially correlated telegraphic noise. In addition to quantum nature of
the heat bath, nonlinearity of the periodic system potential brings in quantum
contribution. We observe that quantization, in general, enhances classical
current at low temperature, while the differences become insignificant at
higher temperature. Interplay of quantum diffusion and quantum correction to
system potential is analyzed for various ranges of temperature, correlation
time and strength of external noise and asymmetry parameters. A possible
experimental realization of the observed quantum effects in a superionic
conductor placed in a random asymmetric dichotomous electric field has been
suggested.Comment: 23 pages and 5 figures. To be published in Physical Review
Noise correlation-induced splitting of Kramers' escape rate from a metastable state
A correlation between two noise processes driving the thermally activated
particles in a symmetric triple well potential, may cause a symmetry breaking
and a difference in relative stability of the two side wells with respect to
the middle one. This leads to an asymmetric localization of population and
splitting of Kramers' rate of escape from the middle well, ensuring a
preferential distribution of the products in the course of a parallel reaction
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