25,367 research outputs found
Lorentz violation in the linearized gravity
We study some consequences of the introduction of a Lorentz-violating
modification term in the linearized gravity, which leads to modified dispersion
relations for gravitational waves in the vacuum. We also discuss possible
mechanisms for the induction of such a term in the Lagrangian.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 201
model in aether-superspace
In this paper we study the dynamical generation of mass in the
Lorentz-violating model defined in two and three-dimensional
aether-superspace. We show that even though the model presents a phase
structure similar to the usual, Lorentz invariant case, the dynamically
generated mass by quantum corrections has a dependence on the Lorentz violating
background properties, except for spacelike LV vector parameter. This is to be
contrasted with the behavior of the quantum electrodynamics in the
two-dimensional aether-superspace, where the dynamical generation of mass was
shown to exhibit an explicit dependence on the aether parameters in every
possible case.Comment: 18 pages, 4 figure
Matrix Models, Argyres-Douglas singularities and double scaling limits
We construct an N=1 theory with gauge group U(nN) and degree n+1 tree level
superpotential whose matrix model spectral curve develops an A_{n+1}
Argyres-Douglas singularity. We evaluate the coupling constants of the
low-energy U(1)^n theory and show that the large N expansion is singular at the
Argyres-Douglas points. Nevertheless, it is possible to define appropriate
double scaling limits which are conjectured to yield four dimensional
non-critical string theories as proposed by Ferrari. In the Argyres-Douglas
limit the n-cut spectral curve degenerates into a solution with n/2 cuts for
even n and (n+1)/2 cuts for odd n.Comment: 31 pages, 1 figure; the expression of the superpotential has been
corrected and the calculation of the coupling constants of the low-energy
theory has been adde
Renormalization Group and Conformal Symmetry Breaking in the Chern-Simons Theory Coupled to Matter
The three-dimensional Abelian Chern-Simons theory coupled to a scalar and a
fermionic field of arbitrary charge is considered in order to study conformal
symmetry breakdown and the effective potential stability. We present an
improved effective potential computation based on two-loop calculations and the
renormalization group equation: the later allows us to sum up series of terms
in the effective potential where the power of the logarithms are one, two and
three units smaller than the total power of coupling constants (i.e., leading,
next-to-leading and next-to-next-to-leading logarithms). For the sake of this
calculation we determined the beta function of the
fermion-fermion-scalar-scalar interaction and the anomalous dimension of the
scalar field. We shown that the improved effective potential provides a much
more precise determination of the properties of the theory in the broken phase,
compared to the standard effective potential obtained directly from the loop
calculations. This happens because the region of the parameter space where
dynamical symmetry breaking occurs is drastically reduced by the improvement
discussed here.Comment: 29 pages, 10 figures, 1 tabl
Renormalization Group Improvement and Dynamical Breaking of Symmetry in a Supersymmetric Chern-Simons-matter Model
In this work, we investigate the consequences of the Renormalization Group
Equation (RGE) in the determination of the effective superpotential and the
study of Dynamical Symmetry Breaking (DSB) in an N = 1 supersymmetric theory
including an Abelian Chern-Simons superfield coupled to N scalar superfields in
(2+1) dimensional spacetime. The classical Lagrangian presents scale
invariance, which is broken by radiative corrections to the effective
superpotential. We calculate the effective superpotential up to two-loops by
using the RGE and the beta functions and anomalous dimensions known in the
literature. We then show how the RGE can be used to improve this calculation,
by summing up properly defined series of leading logs (LL), next-to-leading
logs (NLL) contributions, and so on... We conclude that even if the RGE
improvement procedure can indeed be applied in a supersymmetric model, the
effects of the consideration of the RGE are not so dramatic as it happens in
the non-supersymmetric case.Comment: v4: 11 pages, 1 figure. Version accepted for publication in NP
Dynamical aspects of inextensible chains
In the present work the dynamics of a continuous inextensible chain is
studied. The chain is regarded as a system of small particles subjected to
constraints on their reciprocal distances. It is proposed a treatment of
systems of this kind based on a set Langevin equations in which the noise is
characterized by a non-gaussian probability distribution. The method is
explained in the case of a freely hinged chain. In particular, the generating
functional of the correlation functions of the relevant degrees of freedom
which describe the conformations of this chain is derived. It is shown that in
the continuous limit this generating functional coincides with a model of an
inextensible chain previously discussed by one of the authors of this work.
Next, the approach developed here is applied to a inextensible chain, called
the freely jointed bar chain, in which the basic units are small extended
objects. The generating functional of the freely jointed bar chain is
constructed. It is shown that it differs profoundly from that of the freely
hinged chain. Despite the differences, it is verified that in the continuous
limit both generating functionals coincide as it is expected.Comment: 15 pages, LaTeX 2e + various packages, 3 figures. The title has been
changed and three references have been added. A large part of the manuscript
has been rewritten to improve readability. Chapter 4 has been added. It
contains the construction of the generating functional without the
shish-kebab approximation and a new derivation of the continuous limit of the
freely jointed bar chai
On the validity of the adiabatic approximation in compact binary inspirals
Using a semi-analytical approach recently developed to model the tidal
deformations of neutron stars in inspiralling compact binaries, we study the
dynamical evolution of the tidal tensor, which we explicitly derive at second
post-Newtonian order, and of the quadrupole tensor. Since we do not assume a
priori that the quadrupole tensor is proportional to the tidal tensor, i.e. the
so called "adiabatic approximation", our approach enables us to establish to
which extent such approximation is reliable. We find that the ratio between the
quadrupole and tidal tensors (i.e., the Love number) increases as the inspiral
progresses, but this phenomenon only marginally affects the emitted
gravitational waveform. We estimate the frequency range in which the tidal
component of the gravitational signal is well described using the stationary
phase approximation at next-to-leading post-Newtonian order, comparing
different contributions to the tidal phase. We also derive a semi-analytical
expression for the Love number, which reproduces within a few percentage points
the results obtained so far by numerical integrations of the relativistic
equations of stellar perturbations.Comment: 13 pages, 1 table, 2 figures. Minor changes to match the version
appearing on Phys. Rev.
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