1,817 research outputs found
Black hole collapse simulated by vacuum fluctuations with a moving semi-transparent mirror
Creation of scalar massless particles in two-dimensional Minkowski
space-time--as predicted by the dynamical Casimir effect--is studied for the
case of a semitransparent mirror initially at rest, then accelerating for some
finite time, along a trajectory that simulates a black hole collapse (defined
by Walker, and Carlitz and Willey), and finally moving with constant velocity.
When the reflection and transmission coefficients are those in the model
proposed by Barton, Calogeracos, and Nicolaevici [r(w)=-i\alpha/(\w+i\alpha)
and s(w)=\w/(\w+i\alpha), with ], the Bogoliubov coefficients
on the back side of the mirror can be computed exactly. This allows us to prove
that, when is very large (case of an ideal, perfectly reflecting
mirror) a thermal emission of scalar massless particles obeying Bose-Einstein
statistics is radiated from the mirror (a black body radiation), in accordance
with results previously obtained in the literature. However, when is
finite (semitransparent mirror, a physically realistic situation) the striking
result is obtained that the thermal emission of scalar massless particles obeys
Fermi-Dirac statistics. We also show here that the reverse change of statistics
takes place in a bidimensional fermionic model for massless particles, namely
that the Fermi-Dirac statistics for the completely reflecting situation will
turn into the Bose-Einstein statistics for a partially reflecting, physical
mirror.Comment: 13 pages, no figures, version to appear in Physical Review
Qualitative study in Loop Quantum Cosmology
This work contains a detailed qualitative analysis, in General Relativity and
in Loop Quantum Cosmology, of the dynamics in the associated phase space of a
scalar field minimally coupled with gravity, whose potential mimics the
dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with
the orbits (solutions) of the system, we will see that there are analytic ones,
which lead to the same dynamics as the perfect fluid, and our goal is to check
their stability, depending on the value of the EoS parameter, i.e., to show
whether the other orbits converge or diverge to these analytic solutions at
early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ
Avantprojecte de llei sobre la filiació extramatrimonial. Edició crítica i estudi d'un avantprojecte de llei inèdit de la Comissió Jurídica Assessora de la Generalitat de Catalunya durant la Segona República
En aquest treball es publica l'edició crítica i l'estudi jurídic de l'Avantprojecte de llei
sobre filiació extramatrimonial que elaborà la Comissió Jurídica Assessora de la Generalitat
de Catalunya durant la Segona República espanyola, del qual fins ara només es tenia una
notícia succinta gràcies als escrits de Ramon Maria Roca i Sastre, que fou un dels membres
de la Comissió que destacadament participà en la seva elaboració.This paper presents a critical edition and the respective legal study of the Draft Bill of
Law on Out-of-Wedlock Filiation, which was prepared by the Legal Advisory Commission
of the Government of Catalonia during the Second Spanish Republic. Up to now, only
a succinct knowledge of this text was available through the writings of Ramon Maria Roca
i Sastre, a member of the Commission who played a prominent role in its drafting.En este trabajo se publica la edición crítica y el estudio jurídico del Anteproyecto de
ley sobre filiación extramatrimonial elaborado por la Comissió Jurídica Assessora de laGeneralitat de Catalunya durante la Segunda República española, del que hasta la fecha
solo se tenía una sucinta noticia gracias a los escritos de Ramon Maria Roca i Sastre, uno de
los miembros de la Comissió que descatadamente participó en su elaboración
Constitución catalana y Cortes de Cataluña : Excerpta vuitcentista de peguera, a càrrec de Ramon López Soler
Constitución catalana y Cortes de Cataluña : Excerpta vuitcentista de peguera, a càrrec de Ramon López Soler
Els canvis de l'olfacte en l'embaràs
És cert el que es diu sobre el canvi de les olors en la dona embarassada
Generalized Yukawa couplings and matrix models
In this note we investigate U(N) gauge theories with matter in the
fundamental and adjoint representations of the gauge group, interacting via
generalized Yukawa terms of the form Tr[Q \Phi^n {\tilde Q}]. We find agreement
between the matrix model and the gauge theory descriptions of these theories.
The analysis leads to a partial description of the Higgs branch of the gauge
theory. We argue that the transition between phases with different unbroken
flavor symmetry groups is related to the appearance of cuts in the matrix model
computation
Stochastic quantization and holographic Wilsonian renormalization group
We study relation between stochastic quantization and holographic Wilsonian
renormalization group flow. Considering stochastic quantization of the boundary
on-shell actions with the Dirichlet boundary condition for certain bulk
gravity theories, we find that the radial flows of double trace deformations in
the boundary effective actions are completely captured by stochastic time
evolution with identification of the radial coordinate `' with the
stochastic time '' as . More precisely, we investigate Langevin
dynamics and find an exact relation between radial flow of the double trace
couplings and 2-point correlation functions in stochastic quantization. We also
show that the radial evolution of double trace deformations in the boundary
effective action and the stochastic time evolution of the Fokker-Planck action
are the same. We demonstrate this relation with a couple of examples:
(minimally coupled)massless scalar fields in and U(1) vector fields in
.Comment: 1+30 pages, a new subsection is added, references are adde
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