1,509 research outputs found
The effects of colored quark entropy on the bag pressure
We study the effects of the ground state entropy of colored quarks upon the
bag pressure at low temperatures. The vacuum expectation values of the quark
and gluon fields are used to express the interactions in QCD ground state in
the limit of low temperatures and chemical potentials. Apparently, the
inclusion of this entropy in the equation of state provides the hadron
constituents with an additional heat which causes a decrease in the effective
latent heat inside the hadronic bag and consequently decreases the
non-perturbative bag pressure. We have considered two types of baryonic bags,
and . In both cases we have found that the bag pressure
decreases with the temperature. On the other hand, when the colored quark
ground state entropy is not considered, the bag pressure as conventionally
believed remains constant for finite temperature.Comment: 13 pages, 2 eps-figures (2 parts each
Entropy in quantum chromodynamics
We review the role of zero-temperature entropy in several closely-related
contexts in QCD. The first is entropy associated with disordered condensates,
including . The second is vacuum entropy arising from QCD
solitons such as center vortices, yielding confinement and chiral symmetry
breaking. The third is entanglement entropy, which is entropy associated with a
pure state, such as the QCD vacuum, when the state is partially unobserved and
unknown. Typically, entanglement entropy of an unobserved three-volume scales
not with the volume but with the area of its bounding surface. The fourth
manifestation of entropy in QCD is the configurational entropy of
light-particle world-lines and flux tubes; we argue that this entropy is
critical for understanding how confinement produces chiral symmetry breakdown,
as manifested by a dynamically-massive quark, a massless pion, and a condensate.Comment: 22 pages, 2 figures. Preprint version of invited review for Modern
Physics Letters
Two-mode entanglement in two-component Bose-Einstein condensates
We study the generation of two-mode entanglement in a two-component
Bose-Einstein condensate trapped in a double-well potential. By applying the
Holstein-Primakoff transformation, we show that the problem is exactly solvable
as long as the number of excitations due to atom-atom interactions remains low.
In particular, the condensate constitutes a symmetric Gaussian system, thereby
enabling its entanglement of formation to be measured directly by the
fluctuations in the quadratures of the two constituent components [Giedke {\it
et al.}, Phys. Rev. Lett. {\bf 91}, 107901 (2003)]. We discover that
significant two-mode squeezing occurs in the condensate if the interspecies
interaction is sufficiently strong, which leads to strong entanglement between
the two components.Comment: 22 pages, 4 figure
Topological Order and Quantum Criticality
In this chapter we discuss aspects of the quantum critical behavior that
occurs at a quantum phase transition separating a topological phase from a
conventionally ordered one. We concentrate on a family of quantum lattice
models, namely certain deformations of the toric code model, that exhibit
continuous quantum phase transitions. One such deformation leads to a
Lorentz-invariant transition in the 3D Ising universality class. An alternative
deformation gives rise to a so-called conformal quantum critical point where
equal-time correlations become conformally invariant and can be related to
those of the 2D Ising model. We study the behavior of several physical
observables, such as non-local operators and entanglement entropies, that can
be used to characterize these quantum phase transitions. Finally, we briefly
consider the role of thermal fluctuations and related phase transitions, before
closing with a short overview of field theoretical descriptions of these
quantum critical points.Comment: 24 pages, 7 figures, chapter of the book "Understanding Quantum Phase
Transitions", edited by Lincoln D. Carr (CRC Press / Taylor and Francis,
2010); v2: updated reference
The phase-separation mechanism of a binary mixture in a ring trimer
We show that, depending on the ratio between the inter- and the intra-species
interactions, a binary mixture trapped in a three-well potential with periodic
boundary conditions exhibits three macroscopic ground-state configurations
which differ in the degree of mixing. Accordingly, the corresponding quantum
states feature either delocalization or a Schr\"odinger cat-like structure. The
two-step phase separation occurring in the system, which is smoothed by the
activation of tunnelling processes, is confirmed by the analysis of the energy
spectrum that collapses and rearranges at the two critical points. In such
points, we show that also Entanglement Entropy, a quantity borrowed from
quantum-information theory, features singularities, thus demonstrating its
ability to witness the double mixining-demixing phase transition. The developed
analysis, which is of interest to both the experimental and theoretical
communities, opens the door to the study of the demixing mechanism in complex
lattice geometries.Comment: 14 pages, 9 figure
Black Holes as Quantum Gravity Condensates
We model spherically symmetric black holes within the group field theory
formalism for quantum gravity via generalised condensate states, involving sums
over arbitrarily refined graphs (dual to 3d triangulations). The construction
relies heavily on both the combinatorial tools of random tensor models and the
quantum geometric data of loop quantum gravity, both part of the group field
theory formalism. Armed with the detailed microscopic structure, we compute the
entropy associated with the black hole horizon, which turns out to be
equivalently the Boltzmann entropy of its microscopic degrees of freedom and
the entanglement entropy between the inside and outside regions. We recover the
area law under very general conditions, as well as the Bekenstein-Hawking
formula. The result is also shown to be generically independent of any specific
value of the Immirzi parameter.Comment: 22 page
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