594 research outputs found
Quantum States of String-Inspired Lineal Gravity
We construct quantum states for a (1+1) dimensional gravity-matter model that
is also a gauge theory based on the centrally extended Poincar\'e group.
Explicit formulas are found, which exhibit interesting structures. For example
wave functionals are gauge invariant except for a gauge non-invariant phase
factor that is the Kirillov-Kostant 1-form on the (co-) adjoint orbit of the
group. However no evidence for gravity-matter forces is found.Comment: 23 pages in REVTEX, MIT-CTP-227
Poincar\'e Gauge Theories for Lineal Garvity
We have shown that two of the most studied models of lineal gravities -
Liouville gravity and a ``string-inspired'' model exhibiting the main
characteristic features of a black-hole solution - can be formulated as gauge
invariant theories of the Poincar\'e group. The gauge invariant couplings to
matter (particles, scalar and spinor fields) and explicit solutions for some
matter field configurations, are provided. It is shown that both the models, as
well as the couplings to matter, can be obtained as suitable dimensional
reductions of a 2+1-dimensional ISO(2,1) gauge invariant theory.Comment: TeX Manuscript, 30 page
Extended de Sitter Theory of Two Dimensional Gravitational Forces
We present a simple unifying gauge theoretical formulation of gravitational
theories in two dimensional spacetime. This formulation includes the effects of
a novel matter-gravity coupling which leads to an extended de Sitter symmetry
algebra on which the gauge theory is based. Contractions of this theory
encompass previously studied cases.Comment: 19pp, no figs., CTP 2228, UCONN-93-
String-Inspired Gravity Coupled to Yang-Mills Fields
String-inspired 1+1-dimensional gravity is coupled to Yang-Mills fields in
the Cangemi-Jackiw gauge-theoretical formulation, based on the extended
Poincar\'e group. A family of couplings, which involves metrics obtainable from
the physical metric with a conformal rescaling, is considered, and the
resulting family of models is investigated both at the classical and the
quantum level. In particular, also using a series of Kirillov-Kostant phases,
the wave functionals that solve the constraints are identified.Comment: 15 pages, LaTex
Exact Physical Black Hole States in Generic 2-D Dilaton Gravity
The quantum mechanics of black holes in generic 2-D dilaton gravity is
considered. The Hamiltonian surface terms are derived for boundary conditions
corresponding to an eternal black hole with slices on the interior ending on
the horizon bifurcation point. The quantum Dirac constraints are solved exactly
for these boundary conditions to yield physical eigenstates of the energy
operator. The solutions are obtained in terms of geometrical phase space
variables that were originally used by Cangemi, Jackiw and Zwiebach in the
context of string inspired dilaton gravity. The spectrum is continuous in the
Lorentzian sector, but in the Euclidean sector the thermodynamic entropy must
be where is an integer. The general class of models considered
contains as special cases string inspired dilaton gravity, Jackiw-Teitelboim
gravity and spherically symmetry gravity.Comment: 11 pages, Revte
Topological quantum transition driven by charge-phonon coupling in the Haldane Chern insulator
In condensed matter physics many features can be understood in terms of their
topological properties. Here we report evidence of a topological quantum
transition driven by the charge-phonon coupling in the spinless Haldane model
on a honeycomb lattice, a well-known prototypical model of Chern insulator.
Starting from parameters describing the topological phase in the bare Haldane
model, we show that the increasing of the strength of the charge lattice
coupling drives the system towards a trivial insulator. The average number of
fermions in the Dirac point, characterized by the lowest gap, exhibits a finite
discontinuity at the transition point and can be used as direct indicator of
the topological quantum transition. Numerical simulations show, also, that the
renormalized phonon propagator exhibits a two peak structure across the quantum
transition, whereas, in absence of the mass term in the bare Hadane model,
there is indication of a complete softening of the effective vibrational mode
signaling a charge density wave instability.Comment: 5 pages, 4 figure
Exact Quantum States for all Two-Dimensional Dilaton Gravity Theories
It is shown that the recently obtained quantum wave functionals in terms of
the CJZ variables for generic 2d dilaton gravity are equivalent to the
previously reported exact quantum wave functionals in geometrical variables. A
third representation of these exact quantum states is also presented
A WZW model based on a non-semi-simple group
We present a conformal field theory which desribes a homogeneous four
dimensional Lorentz-signature space-time. The model is an ungauged WZW model
based on a central extension of the Poincar\'e algebra. The central charge of
this theory is exactly four, just like four dimensional Minkowski space. The
model can be interpreted as a four dimensional monochromatic plane wave. As
there are three commuting isometries, other interesting geometries are expected
to emerge via duality.Comment: 8 pages, phyzzx, IASSNS-HEP-93/61 Texable versio
Two channel model for optical conductivity of high mobility organic crystals
We show that the temperature dependence of conductivity of high mobility
organic crystals Pentacene and Rubrene can be quantitatively described in the
framework of the model where carriers are scattered by quenched local
impurities and interact with phonons by Su-Schrieffer-Hegger (SSH) coupling.
Within this model, we present approximation free results for mobility and
optical conductivity obtained by world line Monte Carlo, which we generalize to
the case of coupling both to phonons and impurities. We find fingerprints of
carrier dynamics in these compounds which differ from conventional metals and
show that the dynamics of carriers can be described as a superposition of a
Drude term representing diffusive mobile particles and a Lorentz term
associated with dynamics of localized charges.Comment: 6 pages, 5 figure
Dirac Quantization of Two-Dimensional Dilaton Gravity Minimally Coupled to N Massless Scalar Fields
It is shown that the Callan-Giddings-Harvey-Strominger theory on the cylinder
can be consistently quantized (using Dirac's approach) without imposing any
constraints on the sign of the gravitational coupling constant or the sign (or
value) of the cosmological constant. The quantum constraints in terms of the
original geometrical variables are also derived
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