915 research outputs found
Vacuum Boundary Effects
The effect of boundary conditions on the vacuum structure of quantum field
theories is analysed from a quantum information viewpoint. In particular, we
analyse the role of boundary conditions on boundary entropy and entanglement
entropy. The analysis of boundary effects on massless free field theories
points out the relevance of boundary conditions as a new rich source of
information about the vacuum structure. In all cases the entropy does not
increase along the flow from the ultraviolet to the infrared.Comment: 10 page
Cosmic Rays Induced Background Radiation on Board of Commercial Flights
The aim of this work is to determine the total integrated flux of cosmic
radiation which a commercial aircraft is exposed to along specific flight
trajectories. To study the radiation background during a flight and its
modulation by effects such as altitude, latitude, exposure time and transient
magnetospheric events, we perform simulations based on Magnetocosmics and
CORSIKA codes, the former designed to calculate the geomagnetic effects on
cosmic rays propagation and the latter allows us to simulate the development of
extended air showers in the atmosphere. In this first work, by considering the
total flux of cosmic rays from 5 GeV to 1 PeV, we obtained the expected
integrated flux of secondary particles on board of a commercial airplane during
the Bogot\'a-Buenos Aires trip by point-to-point numerical integration.Comment: 5 pages, 2 figures, Proceedings X SILAFAE Medellin-2014. To appear in
Nuclear Physics B - Proceedings Supplement
Geant4 based simulation of the Water Cherenkov Detectors of the LAGO Project
To characterize the signals registered by the different types of water
Cherenkov detectors (WCD) used by the Latin American Giant Observatory (LAGO)
Project, it is necessary to develop detailed simulations of the detector
response to the flux of secondary particles at the detector level. These
particles are originated during the interaction of cosmic rays with the
atmosphere. In this context, the LAGO project aims to study the high energy
component of gamma rays bursts (GRBs) and space weather phenomena by looking
for the solar modulation of galactic cosmic rays (GCRs). Focus in this, a
complete and complex chain of simulations is being developed that account for
geomagnetic effects, atmospheric reaction and detector response at each LAGO
site. In this work we shown the first steps of a GEANT4 based simulation for
the LAGO WCD, with emphasis on the induced effects of the detector internal
diffusive coating.Comment: 5 pages, 4 figures, Proceedings X SILAFAE Medellin-2014. To appear in
Nuclear Physics B - Proceedings Supplement
Implementing the De-thinning Method for High Energy Cosmic Rays Extensive Air Shower Simulations
To simulate the interaction of cosmic rays with the Earth atmosphere requires
highly complex computational resources and several statistical techniques have
been developed to simplify those calculations. It is common to implement the
thinning algorithms to reduce the number of secondary particles by assigning
weights to representative particles in the evolution of the cascade. However,
since this is a compression method with information loss, it is required to
recover the original flux of secondary particles without introduce artificial
biases. In this work we present the preliminary results of our version of the
de-thinning algorithm for the reconstruction of thinned simulations of
extensive air showers initiated by cosmic rays and photons in the energy range
.Comment: 5 pages, 2 figures, 1 table, Proceedings X SILAFAE Medellin-2014. To
appear in Nuclear Physics B - Proceedings Supplement
Boundary conditions: The path integral approach
The path integral approach to quantum mechanics requires a substantial
generalisation to describe the dynamics of systems confined to bounded domains.
Non-local boundary conditions can be introduced in Feynman's approach by means
of boundary amplitude distributions and complex phases to describe the quantum
dynamics in terms of the classical trajectories. The different prescriptions
involve only trajectories reaching the boundary and correspond to different
choices of boundary conditions of selfadjoint extensions of the Hamiltonian.
One dimensional particle dynamics is analysed in detail.Comment: 8 page
Consistency of the Regularization of Gauge Theories by High Covariant Derivatives
We show that regularization of gauge theories by higher covariant derivatives
and gauge invariant Pauli-Villars regulators is a consistent method if the
Pauli-Villars vector fields are considered in a covariant in the regulating
Pauli-Villars fields is pathological and the original Slavnov proposal in
covariant Landau gauge is not correct because of the appearance of massless
modes in the regulators which do not decouple when the ultraviolet regulator is
removed. In such a case the method does not correspond to the regularization of
a pure gauge theory but that of a gauge theory in interaction with massless
ghost fields. This explains the problems pointed out by Martin and Ruiz in
covariant Landau gauge. However, a minor modification of Slavnov method
provides a consistent regularization even for such a case. The regularization
that we introduce also solves the problem of overlapping divergences in a way
similar to geometric regularization and yields the standard values of the
and functions of the renormalization group equations.Comment: 20 pages, latex, 3 Postscript figures (expanded version
Exact renormalization-group analysis of first order phase transitions in clock models
We analyze the exact behavior of the renormalization group flow in
one-dimensional clock-models which undergo first order phase transitions by the
presence of complex interactions. The flow, defined by decimation, is shown to
be single-valued and continuous throughout its domain of definition, which
contains the transition points. This fact is in disagreement with a recently
proposed scenario for first order phase transitions claiming the existence of
discontinuities of the renormalization group. The results are in partial
agreement with the standard scenario. However in the vicinity of some fixed
points of the critical surface the renormalized measure does not correspond to
a renormalized Hamiltonian for some choices of renormalization blocks. These
pathologies although similar to Griffiths-Pearce pathologies have a different
physical origin: the complex character of the interactions. We elucidate the
dynamical reason for such a pathological behavior: entire regions of coupling
constants blow up under the renormalization group transformation. The flows
provide non-perturbative patterns for the renormalization group behavior of
electric conductivities in the quantum Hall effect.Comment: 13 pages + 3 ps figures not included, TeX, DFTUZ 91.3
Vacuum Energy and Renormalization on the Edge
The vacuum dependence on boundary conditions in quantum field theories is
analysed from a very general viewpoint. From this perspective the
renormalization prescriptions not only imply the renormalization of the
couplings of the theory in the bulk but also the appearance of a flow in the
space of boundary conditions. For regular boundaries this flow has a large
variety of fixed points and no cyclic orbit. The family of fixed points
includes Neumann and Dirichlet boundary conditions. In one-dimensional field
theories pseudoperiodic and quasiperiodic boundary conditions are also RG fixed
points. Under these conditions massless bosonic free field theories are
conformally invariant. Among all fixed points only Neumann boundary conditions
are infrared stable fixed points. All other conformal invariant boundary
conditions become unstable under some relevant perturbations. In finite volumes
we analyse the dependence of the vacuum energy along the trajectories of the
renormalization group flow providing an interesting framework for dark energy
evolution. On the contrary, the renormalization group flow on the boundary does
not affect the leading behaviour of the entanglement entropy of the vacuum in
one-dimensional conformally invariant bosonic theories.Comment: 10 pages, 1 eps figur
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