21,339 research outputs found
Steady-state dynamics and effective temperatures of quantum criticality in an open system
We study the thermal and non-thermal steady state scaling functions and the
steady-state dynamics of a model of local quantum criticality. The model we
consider, i.e. the pseudogap Kondo model, allows us to study the concept of
effective temperatures near fully interacting as well as weak-coupling fixed
points. In the vicinity of each fixed point we establish the existence of an
effective temperature --different at each fixed point-- such that the
equilibrium fluctuation-dissipation theorem is recovered. Most notably,
steady-state scaling functions in terms of the effective temperatures coincide
with the equilibrium scaling functions. This result extends to higher
correlation functions as is explicitly demonstrated for the Kondo singlet
strength. The non-linear charge transport is also studied and analyzed in terms
of the effective temperature.Comment: 5 pages, 4 figures; Supplementary Material (7 pages, 1 figure
Finite size and finite temperature studies of the spin chain
We study a quantum spin chain invariant by the superalgebra . We
derived non-linear integral equations for the row-to-row transfer matrix
eigenvalue in order to analyze its finite size scaling behaviour and we
determined its central charge. We have also studied the thermodynamical
properties of the obtained spin chain via the non-linear integral equations for
the quantum transfer matrix eigenvalue. We numerically solved these NLIE and
evaluated the specific heat and magnetic susceptibility. The analytical low
temperature analysis was performed providing a different value for the
effective central charge. The computed values are in agreement with the
numerical predictions in the literature.Comment: 26 pages, 2 figure
Spatial correlations in parametric down-conversion
The transverse spatial effects observed in photon pairs produced by
parametric down-conversion provide a robust and fertile testing ground for
studies of quantum mechanics, non-classical states of light, correlated imaging
and quantum information. Over the last 20 years there has been much progress in
this area, ranging from technical advances and applications such as quantum
imaging to investigations of fundamental aspects of quantum physics such as
complementarity relations, Bell's inequality violation and entanglement. The
field has grown immensely: a quick search shows that there are hundreds of
papers published in this field. The objective of this article is to review the
building blocks and major theoretical and experimental advances in the field,
along with some possible technical applications and connections to other
research areas.Comment: 116 pages, 35 figures. To appear in Physics Report
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