2,427 research outputs found
Remarks on Screening in a Gauge-Invariant Formalism
In this paper we display a direct and physically attractive derivation of the
screening contribution to the interaction potential in the Chiral Schwinger
model and generalized Maxwell-Chern-Simons gauge theory. It is shown that these
results emerge naturally when a correct separation between gauge-invariant and
gauge degrees of freedom is made. Explicit expressions for gauge-invariant
fields are found.Comment: 13 pages, 1 figure, to appear in PR
Exact Results for Supersymmetric Sigma Models
We show that the metric and Berry's curvature for the ground states of
supersymmetric sigma models can be computed exactly as one varies the Kahler
structure. For the case of these are related to special solutions of
affine toda equations. This allows us to extract exact results (including exact
instanton corrections). We find that the ground state metric is non-singular as
the size of the manifold shrinks to zero thus suggesting that 2d QFT makes
sense even beyond zero radius. In other words it seems that manifolds with zero
size are non-singular as target spaces for string theory (even when they are
not conformal). The cases of and are discussed in more detail.Comment: 9
A solution to the zero-hamiltonian problem in 2-D gravity
The zero-hamiltonian problem, present in reparametrization invariant systems,
is solved for the 2-D induced gravity model. Working with methods developed by
Henneaux et al. we find systematically the reduced phase-space physics,
generated by an {\it effective} hamiltonian obtained after complete gauge
fixing.Comment: 5 pages, revte
Quasinormal modes for the charged Vaidya metric
The scalar wave equation is considered in the background of a charged Vaidya
metric in double null coordinates describing a non-stationary charged
black hole with varying mass and charge . The resulting
time-dependent quasinormal modes are presented and analyzed. We show, in
particular, that it is possible to identify some signatures in the quasinormal
frequencies from the creation of a naked singularity.Comment: 4 pages. Prepared for the proceedings of the Spanish Relativity
meeting (ERE2010), Granada, Spain, September 6-10, 201
Quasinormal modes of d-dimensional spherical black holes with a near extreme cosmological constant
We derive an expression for the quasinormal modes of scalar perturbations in
near extreme d-dimensional Schwarzschild-de Sitter and Reissner-Nordstrom-de
Sitter black holes. We show that, in the near extreme limit, the dynamics of
the scalar field is characterized by a Poschl-Teller effective potential. The
results are qualitatively independent of the spacetime dimension and field
mass.Comment: 5 pages, REVTeX4, version to be published in Physical Review
Quantum Electrodynamics in Two-Dimensions at Finite Temperature. Thermofield Bosonization Approach
The Schwinger model at finite temperature is analyzed using the Thermofield
Dynamics formalism. The operator solution due to Lowenstein and Swieca is
generalized to the case of finite temperature within the thermofield
bosonization approach. The general properties of the statistical-mechanical
ensemble averages of observables in the Hilbert subspace of gauge invariant
thermal states are discussed. The bare charge and chirality of the Fermi
thermofields are screened, giving rise to an infinite number of mutually
orthogonal thermal ground states. One consequence of the bare charge and
chirality selection rule at finite temperature is that there are innumerably
many thermal vacuum states with the same total charge and chirality of the
doubled system. The fermion charge and chirality selection rules at finite
temperature turn out to imply the existence of a family of thermal theta vacua
states parametrized with the same number of parameters as in zero temperature
case. We compute the thermal theta-vacuum expectation value of the mass
operator and show that the analytic expression of the chiral condensate for any
temperature is easily obtained within this approach, as well as, the
corresponding high-temperature behavior
Non- symmetric braneworlds in scalar tensorial gravity
We obtain, via the Gauss-Codazzi formalism, the expression of the effective
Einstein-Brans-Dicke projected equations in a non- symmetric
braneworld scenario which presents hybrid compactification. It is shown that
the functional form of such equations resembles the one in the Einstein's case,
except by the fact that they bring extra informations in the context of exotic
compactifications.Comment: 12 pages, LATEX file, no figures. Accepted for publication in the
European Physical Journal
Quantum equivalence between the self-dual and the Maxwell-Chern-Simons models nonlinearly coupled to U(1) scalar fields
The use of master actions to prove duality at quantum level becomes
cumbersome if one of the dual fields interacts nonlinearly with other fields.
This is the case of the theory considered here consisting of U(1) scalar fields
coupled to a self-dual field through a linear and a quadratic term in the
self-dual field. Integrating perturbatively over the scalar fields and deriving
effective actions for the self-dual and the gauge field we are able to
consistently neglect awkward extra terms generated via master action and
establish quantum duality up to cubic terms in the coupling constant. The
duality holds for the partition function and some correlation functions. The
absence of ghosts imposes restrictions on the coupling with the scalar fields.Comment: 13 pages, no figure
Bi-partite entanglement entropy in integrable models with backscattering
In this paper we generalise the main result of a recent work by J. L. Cardy
and the present authors concerning the bi-partite entanglement entropy between
a connected region and its complement. There the expression of the leading
order correction to saturation in the large distance regime was obtained for
integrable quantum field theories possessing diagonal scattering matrices. It
was observed to depend only on the mass spectrum of the model and not on the
specific structure of the diagonal scattering matrix. Here we extend that
result to integrable models with backscattering (i.e. with non-diagonal
scattering matrices). We use again the replica method, which connects the
entanglement entropy to partition functions on Riemann surfaces with two branch
points. Our main conclusion is that the mentioned infrared correction takes
exactly the same form for theories with and without backscattering. In order to
give further support to this result, we provide a detailed analysis in the
sine-Gordon model in the coupling regime in which no bound states (breathers)
occur. As a consequence, we obtain the leading correction to the sine-Gordon
partition function on a Riemann surface in the large distance regime.
Observations are made concerning the limit of large number of sheets.Comment: 22 pages, 2 figure
- …