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cond-mat/9206001
|
Self Organization and a Dynamical Transition in Traffic Flow Models
|
A simple model that describes traffic flow in two dimensions is studied. A
sharp {\it jamming transition } is found that separates between the low density
dynamical phase in which all cars move at maximal speed and the high density
jammed phase in which they are all stuck. Self organization effects in both
phases are studied and discussed.
| 1992-06-02
| 2009-10-22
|
[
"cond-mat"
] |
Ofer Biham, A. Alan Middleton and Dov Levine
|
cond-mat/9205016
|
C_{60} with O defects: Localized states in the gap and oxygen clustering
|
We propose a Su-Schrieffer-Heeger type electron-phonon model for C_{60} with
O defects and solve by the adiabatic approximation. Two new properties are
obtained. (1) The dimerization becomes weaker around the oxygen. Two localized
states appear deep in the gap. Optical transition between them is allowed. This
accords with the recent optical absorption data. (2) Oxygens are predicted to
cluster on the surface of $\soc$. PACS numbers: 3640, 7155, 6165, 3120P
| 1992-05-28
| 2007-05-23
|
[
"cond-mat"
] |
Kikuo Harigaya (Fundamental Physics Section, Electrotechnical
Laboratory, Japan)
|
cond-mat/9205014
|
Lattice distortion and energy level structures in doped C_{60} and
C_{70} studied with the extended Su-Schrieffer-Heeger model: Polaron
excitations and optical absorption
|
We extend the Su-Schrieffer-Heeger model of polyacetylene to C_{60} and
C_{70} molecules, and solve numerically. The calculations of the undoped
systems agree well with the known results. When the system (C_{60} or C_{70})
is doped with one or two electrons (or holes), the additional charges
accumulate almost along an equatorial line of the molecule. The dimerization
becomes weaker almost along the same line. Two energy levels intrude largely in
the gap. The intrusion is larger in C_{70} than in C_{60}. Therefore,
``polarons'' are predicted in doped buckminster- fullerenes. We calculate
optical absorption coefficient for C_{60} in order to look at how ``polarons''
will be observed. It is predicted that there appears a new peak at the lower
energy than the intergap transition peaks. It is also found that C_{60} and
C_{70} are related mutually with respect to electronical structures as well as
lattice geometries. (to be published in Phys. Rev. B 45, June 15 issue)
| 1992-05-27
| 2007-05-23
|
[
"cond-mat"
] |
Kikuo Harigaya (Fundamental Physics Section, Electrotechnical
Laboratory, Japan)
|
cond-mat/9205015
|
Dynamic scaling and quasi-ordered states in the two dimensional
Swift-Hohenberg equation
|
The process of pattern formation in the two dimensional Swift-Hohenberg
equation is examined through numerical and analytic methods. Dynamic scaling
relationships are developed for the collective ordering of convective rolls in
the limit of infinite aspect ratio. The stationary solutions are shown to be
strongly influenced by the strength of noise. Stationary states for small and
large noise strengths appear to be quasi-ordered and disordered respectively.
The dynamics of ordering from an initially inhomogeneous state is very slow in
the former case and fast in the latter. Both numerical and analytic
calculations indicate that the slow dynamics can be characterized by a simple
scaling relationship, with a characteristic dynamic exponent of $1/4$ in the
intermediate time regime.
| 1992-05-27
| 2009-10-22
|
[
"cond-mat"
] |
K.R. Elder (1), Jorge Vi\~nals (2) and Martin Grant (1) ((1)
Department of Physics, McGill University, Rutherford Building, Montr\'eal,
Qu\'ebec, Canada (2) Supercomputer Computations Research Institute, B-186,
Florida State University, Tallahassee, Florida)
|
cond-mat/9205013
|
Molecular Dynamics Simulation of Compressible Fluid Flow in
Two-Dimensional Channels
|
We study compressible fluid flow in narrow two-dimensional channels using a
novel molecular dynamics simulation method. In the simulation area, an upstream
source is maintained at constant density and temperature while a downstream
reservoir is kept at vacuum. The channel is sufficiently long in the direction
of the flow that the finite length has little effect on the properties of the
fluid in the central region. The simulated system is represented by an
efficient data structure, whose internal elements are created and manipulated
dynamically in a layered fashion. Consequently the code is highly efficient and
manifests completely linear performance in simulations of large systems. We
obtain the steady-state velocity, temperature, and density distributions in the
system. The velocity distribution across the channel is very nearly a quadratic
function of the distance from the center of the channel and reveals velocity
slip at the boundaries; the temperature distribution is only approximately a
quartic function of this distance from the center to the channel. The density
distribution across the channel is non-uniform. We attribute this
non-uniformity to the relatively high Mach number, approximately 0.5, in the
fluid flow. An equation for the density distribution based on simple
compressibility arguments is proposed; its predictions agree well with the
simulation results. Validity of the concept of local dynamic temperature and
the variation of the temperature along the channel are discussed.
| 1992-05-26
| 2009-10-22
|
[
"cond-mat"
] |
M. Sun and C. Ebner (Department of Physics, The Ohio State University,
Columbus, OH)
|
cond-mat/9205012
|
Dispersion of the Third-Order Nonlinear Optical Susceptibility in C_{60}
Calculated with a Tight-Binding Model
|
The frequency dependence of third harmonic generation (THG) in C_{60} is
calculated, making use of a tight-binding model for pi-electrons. The
magnitudes of the THG, about 10^{-12} esu, near zero frequency, agree with
those in experiments for the low-energy region. We can also explain the order
of the magnitude, 10^{-11} esu, around the three-photon resonance peak due to
the lowest allowed excitation, recently measured by Meth et al. At higher
energies, we predict a large enhancement of the THG at 3 omega \sim 6eV as a
result of double resonance enhancement.
| 1992-05-26
| 2007-05-23
|
[
"cond-mat"
] |
Kikuo Harigaya and Shuji Abe (Fundamental Physics Section,
Electrotechnical Laboratory, Japan)
|
cond-mat/9205010
|
Elastic String in a Random Potential
|
We have studied numerically the dynamics of a directed elastic string in a
two-dimensional array of quenched random impurities. The string is driven by a
constant transverse force and thermal fluctuations are neglected. There is a
transition from pinned to unpinned behavior at a critical value $F_T$ of the
driving force. At the transition the average string velocity scales with the
driving force. The scaling is equally well described by a power law $v_d\sim
(F-F_T)^\zeta$, with $\zeta=0.24\pm0.1$, or by a logarithm,
$v_d\sim1/\ln(F-F_T)$. The divergence of the velocity-velocity correlation
length at threshold is characterized by an exponent $\nu=1.05\pm0.1$.
| 1992-05-20
| 2009-10-22
|
[
"cond-mat"
] |
M. Dong, M.C. Marchetti, A. Alan Middleton, V. Vinokur
|
cond-mat/9205011
|
Thermal Rounding of the Charge Density Wave Depinning Transition
|
The rounding of the charge density wave depinning transition by thermal noise
is examined. Hops by localized modes over small barriers trigger
``avalanches'', resulting in a creep velocity much larger than that expected
from comparing thermal energies with typical barriers. For a field equal to the
$T=0$ depinning field, the creep velocity is predicted to have a {\em
power-law} dependence on the temperature $T$; numerical computations confirm
this result. The predicted order of magnitude of the thermal rounding of the
depinning transition is consistent with rounding seen in experiment.
| 1992-05-20
| 2009-10-22
|
[
"cond-mat"
] |
A. Alan Middleton
|
cond-mat/9205009
|
Determinant Representation for time and temperature dependent
correlation functions in the isotropic XY model in the transverse magnetic
field
|
Astymptotics of temperature correlations is the most dificult problem of
stat. mech. Recently it was solved for the impenetrable Bose Gas. The idea is
to represent correlation function as $\tau$ function of calssical completely
integrable differential equation. Now we start to apply this program to
isotropic XY model in the trasnsverse magnetic field. In this paper we are
making first step. We representing correlation function as detrminanat of an
integral operator.
| 1992-05-16
| 2011-06-21
|
[
"cond-mat"
] |
F. Colomo, A. Izergin, V. Korepin, V. Tognetti
|
cond-mat/9205008
|
Metals in high magnetic field: a new universality class of Fermi liquids
|
Parquet equations, describing the competition between superconducting and
density-wave instabilities, are solved for a three-dimensional isotropic metal
in a high magnetic field when only the lowest Landau level is filled. In the
case of a repulsive interaction between electrons, a phase transition to the
density-wave state is found at finite temperature. In the opposite case of
attractive interaction, no phase transition is found. With decreasing
temperature $T$, the effective vertex of interaction between electrons
renormalizes toward a one-dimensional limit in a self-similar way with the
characteristic length (transverse to the magnetic field) decreasing as
$\ln^{-1/6}(\omega_c/T)$ ($\omega_c$ is a cutoff). Correlation functions have
new forms, previously unknown for conventional one-dimensional or
three-dimensional Fermi-liquids.
| 1992-05-14
| 2009-10-22
|
[
"cond-mat"
] |
Victor M. Yakovenko
|
cond-mat/9205007
|
Theory of Thermodynamic Magnetic Oscillations in Quasi-One-Dimensional
Conductors
|
The second order correction to free energy due to the interaction between
electrons is calculated for a quasi-one-dimensional conductor exposed to a
magnetic field perpendicular to the chains. It is found that specific heat,
magnetization and torque oscillate when the magnetic field is rotated in the
plane perpendicular to the chains or when the magnitude of magnetic filed is
changed. This new mechanism of thermodynamic magnetic oscillations in metals,
which is not related to the presence of any closed electron orbits, is applied
to explain behavior of the organic conductor (TMTSF)$_2$ClO$_4$.
| 1992-05-14
| 2009-10-22
|
[
"cond-mat"
] |
Victor M. Yakovenko
|
cond-mat/9205006
|
Quaternion Generalization of the Laughlin State and the Three
Dimensional Fractional QHE
|
The 3D state of strongly correlated electrons is proposed, which in the
external magnetic field $\vec B$ exhibits the fractional quantum Hall effect,
with the zero temperature conductivity tensor $\sigma_{ij} = (e^2/h)(1/m)
\sum_k \epsilon_{ijk} B^k/\mid \vec B\mid $. The analog of Landau and Laughlin
states in 3D are given using quaternion coordinates as generalization of
complex coordinates. We discuss the notion of the fractional statistics in 3D
introduced recently by Haldane.
| 1992-05-06
| 2007-05-23
|
[
"cond-mat"
] |
A. V. Balatsky
|
cond-mat/9205005
|
Z_N Phases in Hot Gauge Theories
|
We argue that the \zn phases of hot gauge theories cannot be realized as a
real system with an Hermitean density matrix.
| 1992-05-06
| 2009-12-30
|
[
"cond-mat"
] |
Wei Chen, Mikhail Dobroliubov, and Gordon Semenoff
|
cond-mat/9205004
|
Low Energy Behavior of Quantum Adsorption
|
We present an exact solution of a 1D model: a particle of incident energy $E$
colliding with a target which is a 1D harmonic ``solid slab'' with $N$ atoms in
its ground state; the Hilbert space of the target is restricted to the ($N+1$)
states with zero or one phonon present. For the case of a short range
interaction, $V(z)$, between the particle and the surface atom supporting a
bound state, an explicit non-perturbative solution of the collision problem is
presented. For finite and large $N$, there is no true sticking but only
so-called Feshbach resonances. A finite sticking coefficient ${\sl s}(E)$ is
obtained by introducing a small phonon decay rate $\eta$ and letting
$N\to\infty$. Our main interest is in the behavior of ${\sl s}(E)$ as $E\to 0$.
For a short range $V(z)$, we find ${\sl s}(E)\sim E^{1/2}$, regardless of the
strength of the particle-phonon coupling. However, if $V(z)$ has a Coulomb
$z^{-1}$ tail, we find ${\sl s}(E)\to\alpha$, where $0 < \alpha < 1$. [A fully
classical calculation gives ${\sl s}(E)\to 1$ in both cases.] We conclude that
the same threshold laws apply to 3D systems of neutral and charged particles
respectively.
| 1992-05-05
| 2007-05-23
|
[
"cond-mat"
] |
D.P. Clougherty and W. Kohn
|
cond-mat/9205003
|
Bilinear Quantum Monte Carlo: Expectations and Energy Differences
|
We propose a bilinear sampling algorithm in Green's function Monte Carlo for
expectation values of operators that do not commute with the Hamiltonian and
for differences between eigenvalues of different Hamiltonians. The integral
representations of the Schroedinger equations are transformed into two
equations whose solution has the form $\psi_a(x) t(x,y) \psi_b(y)$, where
$\psi_a$ and $\psi_b$ are the wavefunctions for the two related systems and
$t(x,y)$ is a kernel chosen to couple $x$ and $y$. The Monte Carlo process,
with random walkers on the enlarged configuration space $x \otimes y$, solves
these equations by generating densities whose asymptotic form is the above
bilinear distribution. With such a distribution, exact Monte Carlo estimators
can be obtained for the expectation values of quantum operators and for energy
differences. We present results of these methods applied to several test
problems, including a model integral equation, and the hydrogen atom.
| 1992-05-03
| 2010-01-12
|
[
"cond-mat"
] |
Shiwei Zhang and M.H. Kalos
|
cond-mat/9205001
|
Coulomb drag between two-dimensional electron systems
|
The Coulomb contribution to the temperature-dependent rate of momentum
transfer, $1/\tau_D$, between two electron systems in parallel layers is
determined by setting up two coupled Boltzmann equations, with the boundary
condition that no current flows in the layer where an induced voltage is
measured. The effective Coulomb interaction between the layers is determined
selfconsistently, allowing for the finite thickness of the layers. As
$T\rightarrow 0$, we find that $1/\tau_DT^2$ approaches a constant value. At
higher temperatures $1/\tau_DT^2$ exhibits a maximum at $T=T_{\rm max}$ and
then decreases as $1/T$ with increasing temperature. The value of $T_{\rm max}$
depends on the layer separation $d$ according to $T_{\rm max}\propto
d^{-\alpha}$, where $\alpha\simeq 0.8$. The overall magnitude of the calculated
$1/\tau_D$ is approximately one half of the results of a recent experiment,
suggesting that other mechanisms of momentum transfer may be important.
| 1992-05-01
| 2009-10-22
|
[
"cond-mat"
] |
Antti-Pekka Jauho and Henrik Smith
|
cond-mat/9205002
|
Roughening of Reconstructed Crystal Surfaces and the Hubbard Model
|
We consider a model of a reconstructed crystal surface, first considered by
Villain and Vilfan (Europhys. Lett. 12, p. 523 (1990) and Surf. Sci. 257, p.
368 (1991)) for the gold (110) surface, in which roughening occurs via the
formation of anisotropic steps traversing the entire length of the crystal. The
model is studied by a mapping to a spin--1/2 Fermion system in 1+1 dimensions,
which, in the absence of islands, is precisely the Hubbard model. We consider a
general $\pbyo$ reconstruction, in the presence of inter--step interactions and
closed islands. Our analysis predicts the existence of a new type of rough
phase, with incommensurate correlations in the reconstruction order parameter
and unusual momentum space singularities at a characteristic ``Fermi momentum''
and its harmonics, analagous to the Luttinger liquid of one--dimensional
Fermions. The general phase structure for $p>1$ is as follows: for $p>2$, there
is a flat ordered (FO), a rough incommensurate (RI), and a flat incommensurate
phase (FI). The FO--RI and FO--FI transitions are of the commensurate to
incommensurate type, and the FI--RI transition is in the Kosterlitz--Thouless
(KT) universality class. For $p=2$, the FI phase is replaced by a flat
disordered phase (FD), and there may be a new rough disordered phase (RD). The
FO--FD transition is now of Ising type, and the FD--RD and RI--RD transitions
are in the KT universality class.
| 1992-05-01
| 2007-05-23
|
[
"cond-mat"
] |
Leon Balents and Mehran Kardar
|
cond-mat/9204018
|
Absence of Dipole Transitions in Vortices of Type II Superconductors
|
The response of a single vortex to a time dependent field is examined
microscopically and an equation of motion for vortex motion at non-zero
frequencies is derived. Of interest are frequencies near $\Delta^{2}/E_{F}$,
where $\Delta$ is the bulk energy gap and $E_{F}$ is the fermi energy. The low
temperature, clean, extreme type II limit and maintaining of equilibrium with
the lattice are assumed. A simplification occurs for large planar mass
anisotropy. Thus the results may be pertinent to materials such as $NbSe_2$ and
high temperature superconductors. The expected dipole transition between core
states is hidden because of the self consistent nature of the vortex potential.
Instead the vortex itself moves and has a resonance at the frequency of the
transition.
| 1992-04-30
| 2009-10-22
|
[
"cond-mat"
] |
Theodore C. Hsu (CRTBT-CNRS, Grenoble France)
|
cond-mat/9204017
|
On Models with Inverse-Square Exchange
|
A one-dimensional quantum N-body system of either fermions or bosons with
$SU(n)$ colors interacting via inverse-square exchange is presented in this
article. A class of eigenstates of both the continuum and lattice version of
the model Hamiltonians is constructed in terms of the Jastrow-product type wave
function. The class of states we construct in this paper corresponds to the
ground state and the low energy excitations of the model that can be described
by the effective harmonic fluid Hamiltonian. By expanding the energy about the
ground state we find the harmonic fluid parameters (i.e. the charge, spin
velocities, etc.), explicitly. The correlation exponent and the compressibility
of are also found. As expected the general harmonic relation(i.e.
$v_S=(v_Nv_J)^{1/2}$) is satisfied among the charge and spin velocities.
| 1992-04-29
| 2009-10-22
|
[
"cond-mat"
] |
Z.N.C. Ha and F.D.M. Haldane
|
cond-mat/9204014
|
Blockspin Cluster Algorithms for Quantum Spin Systems
|
Cluster algorithms are developed for simulating quantum spin systems like the
one- and two-dimensional Heisenberg ferro- and anti-ferromagnets. The
corresponding two- and three-dimensional classical spin models with four-spin
couplings are maped to blockspin models with two-blockspin interactions.
Clusters of blockspins are updated collectively. The efficiency of the method
is investigated in detail for one-dimensional spin chains. Then in most cases
the new algorithms solve the problems of slowing down from which standard
algorithms are suffering.
| 1992-04-28
| 2009-10-22
|
[
"cond-mat"
] |
U.-J. Wiese and H.-P. Ying
|
cond-mat/9204015
|
Logarithmically slow domain growth in nonrandomly frustrated systems:
Ising models with competing interactions
|
It is known that in systems which contain randomness explicitly in their
Hamiltonians (e.g., due to impurities), the characteristic size L of the
ordered domains can grow only logarithmically with time t following a quench
below the transition temperature. However, in systems without such imposed
randomness, much faster power law growth has generally been predicted.
Motivated by the slow dynamics present in glasses, we have been looking for
counterexamples, i.e., for models without randomness which nonetheless order
logarithmically slowly. Here, we discuss two closely related models for which
we have simple physical arguments that such slow growth occurs. The basis of
these arguments is the claim that the free energy barriers to domain growth in
these models are proportional to L. Thus, the barriers grow as the domains
coarsen. We present the results of Monte Carlo simulations, which lend strong
support to our claims of growing barriers and logarithmically slow dynamics.
Finally, we discuss how quickly the system orders when it is cooled
continuously through the transition (rather than quenched).
| 1992-04-28
| 2009-10-22
|
[
"cond-mat"
] |
Joel D. Shore, Mark Holzer, and James P. Sethna
|
cond-mat/9204016
|
Logarithmically slow domain growth in nonrandomly frustrated systems---
A summary of the major results
|
Here, we summarize the most important results of our study of logarithmically
slow growth of domains following a quench in two models without randomness in
their Hamiltonians.
This is a slightly updated version of a paper to appear in the Proceedings of
the 1st Annual Tohwa University International Symposium, Fukuoka, Japan
(American Institute of Physics, 1992). It is meant to serve as a brief summary
of cond-mat/9204015 for those who do not wish to read all the details contained
therein (and don't want to hassle with 2 MBytes of tex/ps files).
| 1992-04-28
| 2016-08-31
|
[
"cond-mat"
] |
Joel D. Shore, James P. Sethna, Mark Holzer, and Veit Elser
|
cond-mat/9204013
|
Beyond the ``principle of local symmetry'': derivation of a general
crack propagation law
|
We derive a general crack propagation law for slow brittle cracking, in two
and three dimensions, using symmetry, gauge invariance, and gradient
expansions. Our derivation provides explicit justification for the ``principle
of local symmetry,'' which has been used extensively to describe two
dimensional crack growth, but goes beyond that principle to describe three
dimensional crack phenomena as well. We also find that there are new materials
properties needed to describe the growth of general cracks in three dimensions,
besides the fracture toughness and elastic constants previously used to
describe cracking.
| 1992-04-24
| 2009-10-22
|
[
"cond-mat"
] |
Jennifer Hodgdon and James P. Sethna
|
cond-mat/9204012
|
Tweed in Martensites: A Potential New Spin Glass
|
We've been studying the ``tweed'' precursors above the martensitic transition
in shape--memory alloys. These characteristic cross--hatched modulations occur
for hundreds of degrees above the first--order shape--changing transition. Our
two--dimensional model for this transition, in the limit of infinite elastic
anisotropy, can be mapped onto a spin--glass Hamiltonian in a random field. We
suggest that the tweed precursors are a direct analogy of the spin--glass
phase. The tweed is intermediate between the high--temperature cubic phase and
the low--temperature martensitic phase in the same way as the spin--glass phase
can be intermediate between ferromagnet and antiferromagnet.
| 1992-04-23
| 2015-06-25
|
[
"cond-mat"
] |
James P. Sethna, Sivan Kartha, Teresa Cast'an, and James A. Krumhansl
|
cond-mat/9204011
|
Fredholm Determinant Representation for Correlation Functions in XXO
Heisenberg Chain
|
Space and time dependent temepreture correlation fucntions in the Hiesenberg
XXO chain are evaluated in the magnetic field. The other name of the model is
isotropic xy model in the transverse magnetic field. In the thermodynamic limit
correlations in the model are represented as Fredhom determinanat. We expect
this to to solve the problem of evaluation of asymptotics of temperature
correlations.
| 1992-04-22
| 2008-02-03
|
[
"cond-mat"
] |
F.Colomo, A.G. Izergin, V. Korepin
|
cond-mat/9204010
|
Meissner Effect and Constraints
|
We notice some beautiful geometrical defects found in liquid crystals, and
explain them by imposing a constraint. We study the way constraints can occur,
and introduce the concept of massive fields. We develop the theory of magnetic
field expulsion in superconductors as an example. We notice strong analogies
with the formation of grain boundaries in crystals, and realize that we do not
understand crystals very deeply
| 1992-04-22
| 2008-02-03
|
[
"cond-mat"
] |
James P. Sethna, Ming Huang
|
cond-mat/9204009
|
Order Parameters, Broken Symmetry, and Topology
|
We introduce the theoretical framework we use to study the bewildering
variety of phases in condensed--matter physics. We emphasize the importance of
the breaking of symmetries, and develop the idea of an order parameter through
several examples. We discuss elementary excitations and the topological theory
of defects.
| 1992-04-22
| 2009-09-25
|
[
"cond-mat"
] |
James P. Sethna
|
cond-mat/9204008
|
Image of the Energy Gap Anisotropy in the Vibrational Spectum of a High
Temperature Superconductor
|
We present a new method of determining the anisotropy of the gap function in
layered high-Tc superconductors. Careful inelastic neutron scattering
measurements at low temperature of the phonon dispersion curves in the (100)
direction in La_(1.85)Sr_(.15)CuO_4 would determine whether the gap is
predominately s-wave or d-wave. We also propose an experiment to determine the
gap at each point on a quasi-two-dimensional Fermi surface.
| 1992-04-21
| 2009-10-22
|
[
"cond-mat"
] |
Michael E. Flatte
|
cond-mat/9204007
|
Theory of Directed Polymers
|
We develop a theory of polymers in a nematic solvent by exploiting an analogy
with two-dimensional quantum bosons at zero temperature. We argue that the
theory should also describe polymers in an {\sl isotropic} solvent. The dense
phase is analyzed in a Bogoliubov-like approximation, which assumes a broken
symmetry in the phase of the boson order parameter. We find a stiffening of the
longitudinal fluctuations of the nematic field, calculate the density-density
correlation function, and extend the analysis to the case of ferro- and
electrorheological fluids. The boson formalism is used to derive a simple
hydrodynamic theory which is indistinguishable from the corresponding theory of
polymer nematics in an isotropic solvent at long wavelengths. We also use
hydrodynamics to discuss the physical meaning of the boson order parameter. A
renormalization group treatment in the dilute limit shows that logarithmic
corrections to polymer wandering, predicted by de Gennes, are unaffected by
interpolymer interactions. A continuously variable Flory exponent appears for
polymers embedded in a {\sl two}-dimensional nematic solvent. We include free
polymer ends and hairpin configurations in the theory and show that hairpins
are described by an Ising-like symmetry-breaking term in the boson field
theory.
| 1992-04-14
| 2009-10-22
|
[
"cond-mat"
] |
R.D. Kamien, P. Le Doussal, and D.R. Nelson
|
cond-mat/9204006
|
Chirality Ordering of Chiral Spin Liquids
|
We study the effect of introducing a weak antiferromagnetic interplanar
exchange coupling in the two dimensional frustrated Heisenberg model. We show
that a ferromagnetic(FM) ordering of chirality - {\it i.e.}, same chirality on
adjacent planes - is energetically favoured, thus leading to bulk violation of
the discrete symmetries parity($P$) and time reversal($T$).
| 1992-04-14
| 2009-10-22
|
[
"cond-mat"
] |
D. M. Gaitonde, Dileep P. Jatkar and Sumathi Rao
|
cond-mat/9204005
|
Investigations of Pairing in Anyon Systems
|
We investigate pairing instabilities in the Fermi-liquid-like state of a
single species of anyons. We describe the anyons as Fermions interacting with a
Chern-Simons gauge field and consider the weak coupling limit where their
statistics approaches that of Fermions. We show that, within the conventional
BCS approach, due to induced repulsive Coulomb and current-current
interactions, the attractive Aharonov-Bohm interaction is not sufficient to
generate a gap in the Fermion spectrum.
| 1992-04-13
| 2009-10-22
|
[
"cond-mat"
] |
M.I.Dobroliubov, I.I.Kogan, and G.W.Semenoff
|
cond-mat/9204004
|
Physics beyond quasi-particles: Spectrum and completeness of the 3 state
superintegrable chiral Potts model
|
We find the rules which count the energy levels of the 3 state
superintegrable chiral Potts model and demonstrate that these rules are
complete. We then derive the complete spectrum of excitations in the
thermodynamic limit in the massive phase and demonstrate the existence of
excitations which do not have a quasi-particle form. The physics of these
excitations is compared with the BCS superconductivity spectrum and the
counting rules are compared with the closely related $S=1$ XXZ spin chain.
| 1992-04-13
| 2007-05-23
|
[
"cond-mat"
] |
Srinandan Dasmahapatra, Rinat Kedem and Barry M. McCoy
|
cond-mat/9204003
|
A novel class of singlet superconductors
|
A new class of singlet superconductors with a gap function $\Delta(\bk,
\omega_n)$ which is {\it odd} in both momentum and Matsubara frequency is
considered. Some of the physical properties of this superconductivity are
discussed and it is argued that: i) the electron-phonon interaction can produce
this kind of pairing, ii) in many cases there is no gap in the quasiparticle
spectrum, iii) these superconductors will exhibit a Meissner effect.
| 1992-04-10
| 2007-05-23
|
[
"cond-mat"
] |
Alexander Balatsky and Elihu Abrahams
|
cond-mat/9204002
|
Spin Singlet Quantum Hall Effect and Nonabelian Landau-Ginzburg Theory
|
We show that the Halperin-Haldane SQHE wave function can be written in the
form of a product of a wave function for charged semions in a magnetic field
and a wave function for the Chiral Spin Liquid of neutral spin-$\12$ semions.
We introduce field-theoretic model in which the electron operators are
factorized in terms of charged spinless semions (holons) and neutral spin-$\12$
semions (spinons). Broken time reversal symmetry and short ranged spin
correlations lead to $SU(2)_{k=1}$ Chern-Simons term in Landau-Ginzburg action
for SQHE phase. We construct appropriate coherent states for SQHE phase and
show the existence of $SU(2)$ valued gauge potential. This potential appears as
a result of ``spin rigidity" of the ground state against any displacements of
nodes of wave function from positions of the particles and reflects the
nontrivial monodromy in the presence of these displacements. We argue that
topological structure of $SU(2)_{k=1}$ Chern-Simons theory unambiguously
dictates {\it semion} statistics of spinons.
| 1992-04-10
| 2015-06-25
|
[
"cond-mat"
] |
Alexander Balatsky (Los Alamos National Laboratory)
|
cond-mat/9204001
|
Universal quantum critical dynamics of two-dimensional antiferromagnets
|
The universal dynamic and static properties of two dimensional
antiferromagnets in the vicinity of a zero-temperature phase transition from
long-range magnetic order to a quantum disordered phase are studied. Random
antiferromagnets with both N\'{e}el and spin-glass long-range magnetic order
are considered. Explicit quantum-critical dynamic scaling functions are
computed in a 1/N expansion to two-loops for certain non-random, frustrated
square lattice antiferromagnets. Implications for neutron scattering
experiments on the doped cuprates are noted.
| 1992-04-10
| 2009-10-22
|
[
"cond-mat"
] |
Subir Sachdev and Jinwu Ye
|
cond-mat/9603180
|
Lack of Self-affinity and Anomalous Roughening in Growth Processes
|
We contrast analytical results of a variety of growth models involving
subdiffusion, thermal noise and quenched disorder with simulations of these
models, concluding that the assumed self-affinity property is more an exception
than a rule. In our two dimensional models, self-affine surfaces may only
appear when the roughness exponent is $\chi = 1/2$ or $\chi = 1$. A new scaling
picture, which leads to more suitable ways of determining the scaling
exponents, is proposed when lack of self-affinity exists.
| 1992-03-28
| 2016-08-15
|
[
"cond-mat"
] |
Juan M. L\'opez and Miguel A. Rodr\'iguez (Instituto de Fisica de
Cantabria CSIC-UC, Spain)
|
cs/9301116
|
The problem of compatible representatives
|
The purpose of this note is to attach a name to a natural class of
combinatorial problems and to point out that this class includes many important
special cases. We also show that a simple problem of placing nonoverlapping
labels on a rectangular map is NP-complete.
| 1992-07-01
| 2008-02-03
|
[
"cs.DS",
"math.CO"
] |
Donald E. Knuth, Arvind Raghunathan
|
funct-an/9212005
|
A Fredholm Operator Approach To Morita Equivalence
|
Given C*-algebras A and B and an imprimitivity A-B-bimodule X, we construct
an explicit isomorphism X_* : K_i(A) --> K_i(B) where K_i denote the complex
K-theory functors for i=0, 1. Our techniques do not require separability nor
existence of countable approximate identities. We thus extend, to general
C*-algebras, the result of Brown, Green and Rieffel according to which strongly
Morita equivalent C*-algebras have isomorphic K-groups. The method employed
includes a study of Fredholm operators on Hilbert modules.
| 1992-12-31
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Ruy Exel
|
funct-an/9212004
|
The Soft Torus II: A Variational Analysis of Commutator Norms
|
The field of C*-algebras over the interval [0,2] for which the fibers are the
Soft Tori is shown to be continuous. This result is applied to show that any
pair of non-commuting unitary operators can be perturbed (in a weak sense) in
such a way to decrease the commutator norm. Perturbations in norm are also
considered and a characterization is given for pairs of unitary operators which
are local minimum points for the commutator norm in the finite dimensional
case.
| 1992-12-19
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Ruy Exel
|
funct-an/9212003
|
Compression Limit Algebras
|
This paper studies direct limits of full upper triangular matrix algebras
with embeddings which are not *-extendible. A representation of the limit
algebra is found so that the generated C*-algebra is the C*-envelope. Some
examples are described.
| 1992-12-18
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Alan Hopenwasser, Cecelia Laurie
|
funct-an/9212002
|
On von Neumann algebras which are complemented subspaces of B(H)
|
If there exists a completely bounded projection of B(H) onto a von Neumann
algebra M on H, then M is injective. If there exists a bounded projection and M
is properly infinite, the same conclusion holds.
| 1992-12-14
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Erik Christensen and Allan M. Sinclair
|
funct-an/9212001
|
The free abelian topological group and the free locally convex space on
the unit interval
|
We give a complete description of the topological spaces $X$ such that the
free abelian topological group $A(X)$ embeds into the free abelian topological
group $A(I)$ of the closed unit interval. In particular, the free abelian
topological group $A(X)$ of any finite-dimensional compact metrizable space $X$
embeds into $A(I)$. The situation turns out to be somewhat different for free
locally convex spaces. Some results for the spaces of continuous functions with
the pointwise topology are also obtained. Proofs are based on the classical
Kolmogorov's Superposition Theorem.
| 1992-12-11
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
A.G. Leiderman, S.A. Morris and V.G. Pestov
|
funct-an/9211014
|
Non-commutative spheres and numerical quantum mechanics
|
We discuss some basic issues that arise when one attempts to model quantum
mechanical systems on a computer, and we describe the mathematical structure of
the resulting discretized cannonical commutation relations.
| 1992-11-30
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
William Arveson
|
funct-an/9211015
|
Discretized CCR algebras
|
We discuss how the canonical commutation relations must be modified in order
to make appropriate numerical models of quantum systems. The C*-algebras
associated with the discretized CCRs are the non-commutative spheres of
Bratteli, Elliott, Evans and Kishimoto.
| 1992-11-30
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
William Arveson
|
funct-an/9211012
|
Interpolated free group factors
|
The interpolated free group factors L(F_r), 1 < r <= \infty, are defined and
proofs of their properties with respect to compression by projections and
taking free products are proved. Hence it follows that all the free group
factor are isomorphic to each other or none of them are. These factors were
defined and these properties were proved independently by F. Radulescu, and
those given in this paper are equivalent, but use different techniques.
Specifically, we develop algebraic techniques that allow us to show that R*R =
L(F_2), where R is the hyperfinite II_1 factor.
| 1992-11-28
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Ken Dykema
|
funct-an/9211013
|
Free products of hyperfinite von Neumann algebras and free dimension
|
The free product of an arbitrary pair of finite hyperfinite von Neumann
algebras is examined, and the result is determined to be the direct sum of a
finite dimensional algebra and an interpolated free group factor $L(\freeF_r)$.
The finite dimensional part depends on the minimal projections of the original
algebras and the "dimension", r, of the free group factor part is found using
the notion of free dimension. For discrete amenable groups $G$ and $H$ this
implies that the group von Neumann algebra $L(G*H)$ is an interpolated free
group factor and depends only on the orders of $G$ and $H$.
| 1992-11-28
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Ken Dykema
|
funct-an/9211011
|
On certain free product factors via an extended matrix model
|
Voiculescu's random matrix model for freeness is extended to the non-Gaussian
case and also the case of constant block diagonal matrices. Thus we are able to
investigate free products of free group factors with matrix algebras and with
the hyperfinite II$_1$ factor, showing that $$ L(F_n) * R = L(F_(n+1)) $$ for
$n \ge 1$, (where $L(F_1)=L(Z)$).
| 1992-11-28
| 2016-08-31
|
[
"funct-an",
"math.OA"
] |
Ken Dykema
|
funct-an/9211009
|
Spectral Invariance of Dense Subalgebras of Operator Algebras
|
We define the notion of strong spectral invariance for a dense Frechet
subalgebra A of a Banach algebra B. We show that if A is strongly spectral
invariant in a C*-algebra B, and G is a compactly generated polynomial growth
Type R Lie group, not necessarily connected, then the smooth crossed product
G\rtimes A is spectral invariant in the C*-crossed product G\rtimes B. Examples
of such groups are given by finitely generated polynomial growth discrete
groups, compact or connected nilpotent Lie groups, the group of Euclidean
motions on the plane, the Mautner group, or any closed subgroup of one of
these. Our theorem gives the spectral invariance of G\rtimes A if A is the set
of C^{\infty}-vectors for the action of G on B, or if B= C_{0}(M), and A is a
set of G-differentiable Schwartz functions S(M) on M. This gives many examples
of spectral invariant dense subalgebras for the C*-algebras associated with
dynamical systems. We also obtain relevant results about exact sequences,
subalgebras, tensoring by smooth compact operators, and strong spectral
invariance in L_{1}(G, B).
| 1992-11-27
| 2016-02-15
|
[
"funct-an",
"math.OA"
] |
Larry B. Schweitzer
|
funct-an/9211010
|
Dense m-convex Frechet Subalgebras of Operator Algebra Crossed Products
by Lie Groups
|
Let A be a dense Frechet *-subalgebra of a C*-algebra B. (We do not require
Frechet algebras to be m-convex.) Let G be a Lie group, not necessarily con-
nected, which acts on both $A$ and B by *-automorphisms, and let \s be a sub-
multiplicative function from G to the nonnegative real numbers. If \s and the
action of G on A satisfy certain simple properties, we define a dense Frechet
*-subalgebra G\rtimes^{\s} A of the crossed product L^{1}(G, B). Our algebra
consists of differentiable A-valued functions on G, rapidly vanishing in \s.
We give conditions on the action of G on A which imply the m-convexity of the
dense subalgebra G\rtimes^{\s}A. A locally convex algebra is said to be m-con-
vex if there is a family of submultiplicative seminorms for the topology of the
algebra. The property of m-convexity is important for a Frechet algebra, and is
useful in modern operator theory.
If G acts as a transformation group on a manifold M, we develop a class of
dense subalgebras for the crossed product L^{1}(G, C_{0}(M)), where C_{0}(M)
denotes the continuous functions on M vanishing at infinity with the sup norm
topology.We define Schwartz functions S(M) on M, which are differentiable with
respect to some group action on M, and are rapidly vanishing with respect to
some scale on M. We then form a dense m-convex Frechet *-subalgebra G\rtimes^
{\s} S(M) of rapidly vanishing, G-differentiable functions from G to S(M).
If the reciprocal of \s is in L^{p}(G) for some p, we prove that our group
algebras S^{\s}(G) are nuclear Frechet spaces, and that G\rtimes^{\s}A is the
projective completion S^{\s}(G) \otimes A.
| 1992-11-27
| 2016-02-15
|
[
"funct-an",
"math.OA"
] |
Larry B. Schweitzer
|
funct-an/9211008
|
An analytic structure emerging in presence of infinitely many odd
coordinates
|
This is a contribution to the program of featuring even geometry as a
``collective effect in infinite-dimensional odd geometry,'' as suggested by
Manin. We show that the (Gel'fand) spectrum of the locally convex nonstandard
hull (in the sense of Luxemburg) of a grassmannian algebra with infinitely many
odd generators contains a nontrivial analytic part.
| 1992-11-27
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Vladimir G. Pestov
|
funct-an/9211007
|
Representable K-theory of Smooth Crossed Products by R and Z
|
We show that the Thom isomorphism and the Pimsner-Voiculescu exact sequence
both hold for smooth crossed products of Frechet algebras by R and Z
respectively. We also obtain the same results for L^{1}-crossed products of
Banach algebras by R and Z.
| 1992-11-25
| 2016-02-15
|
[
"funct-an",
"math.OA"
] |
N. Christopher Phillips and Larry B. Schweitzer
|
funct-an/9211005
|
A Short Proof that $M_{n}(A)$ is local if $A$ is local and Fr\'echet
|
We give a short and very general proof of the fact that the property of a
dense Fr\'echet subalgebra of a Banach algebra being local, or closed under the
holomorphic functional calculus in the Banach algebra, is preserved by
tensoring with the $n\times n$ matrix algebra of the complex numbers.
| 1992-11-25
| 2016-02-12
|
[
"funct-an",
"math.OA"
] |
Larry B. Schweitzer
|
funct-an/9211006
|
A Non-Spectral Dense Banach Subalgebra of the Irrational Rotation
Algebra
|
We give an example of a dense, simple, unital Banach subalgebra $A$ of the
irrational rotation C*-algebra $B$, such that $A$ is not a spectral subalgebra
of $B$. This answers a question posed in T.W. Palmer's paper [1].
| 1992-11-25
| 2016-02-15
|
[
"funct-an",
"math.OA"
] |
Larry B. Schweitzer
|
funct-an/9211004
|
Approximately Finite C*-Algebras and Partial Automorphisms
|
We prove that every AF-algebra is isomorphic to a crossed product of a
commutative AF-algebra by a partial automorphism. The case of UHF-algebras is
treated in detail.
| 1992-11-24
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Ruy Exel
|
funct-an/9211003
|
Improper filtrations for C*-algebras: spectra of unilateral tridiagonal
operators
|
We extend the results of our previous paper "C*-algebras and numerical linear
algebra" to cover the case of "unilateral" sections. This situation bears a
close resemblance to the case of Toeplitz operators on Hardy spaces, in spite
of the fact that the operators here are far from Toeplitz operators. In
particular, there is a short exact sequence 0 --> K --> A --> B --> 0 whose
properties are essential to the problem of computing the spectra of self
adjoint operators.
| 1992-11-23
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
William Arveson
|
funct-an/9211002
|
C*-algebras and numerical linear algebra
|
We consider problems associated with the computation of spectra of
self-adjoint operators in terms of the eigenvalue distributions of their n x n
sections. Under rather general circumstances, we show how these eigenvalues
accumulate near points of the essential spectrum of the given operator, and we
prove that their averages converge to a measure concentrated precisely on the
essential spectrum.
In the primary cases of interest, namely the discretized Hamiltonians of
one-dimensional quantum systems, this limiting measure is associated with a
tracial state on a certain simple C*-algebra. These results have led us to
conclude that one must view this kind of numerical analysis in the context of
C*-algebras.
| 1992-11-22
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
William Arveson
|
funct-an/9211001
|
Circle Actions on C*-Algebras, Partial Automorphisms and a Generalized
Pimsner-Voiculescu Exact Sequence
|
We introduce a method to study C*-algebras possessing an action of the circle
group, from the point of view of its internal structure and its K-theory. Under
relatively mild conditions our structure Theorem shows that any C*-algebra,
where an action of the circle is given, arises as the result of a construction
that generalizes crossed products by the group of integers.
Such a generalized crossed product construction is carried out for any
partial automorphism of a C*-algebra, where by a partial automorphism we mean
an isomorphism between two ideals of the given algebra.
Our second main result is an extension to crossed products by partial
automorphisms, of the celebrated Pimsner-Voiculescu exact sequence for
K-groups.
The representation theory of the algebra arising from our construction is
shown to parallel the representation theory for C*-dynamical systems. In
particular, we generalize several of the main results relating to regular and
covariant representations of crossed products.
| 1992-11-22
| 2016-08-31
|
[
"funct-an",
"math.OA"
] |
Ruy Exel
|
funct-an/9209001
|
Extremal Selections of Multifunctions Generating a Continuous Flow
|
Let $F:[0,T]\times\R^n\mapsto 2^{\R^n}$ be a continuous multifunction with
compact, not necessarily convex values. In this paper, we prove that, if $F$
satisfies the following Lipschitz Selection Property: \begin{itemize}
\item[{(LSP)}] {\sl For every $t,x$, every $y\in \overline{co} F(t,x)$ and
$\varepsilon>0$, there exists a Lipschitz selection $\phi$ of $\overline{co}F$,
defined on a neighborhood of $(t,x)$, with $|\phi(t,x)-y|<\varepsilon$.}
\end{itemize} then there exists a measurable selection $f$ of $ext F$\ such
that, for every $x_0$, the Cauchy problem $$ \dot x(t)=f(t,x(t)),\qquad\qquad
x(0)=x_0 $$ has a unique Caratheodory solution, depending continuously on
$x_0$. We remark that every Lipschitz multifunction with compact values
satisfies (LSP). Another interesting class, for which (LSP) holds, consists of
those continuous multifunctions $F$ whose values are compact and have convex
closure with nonempty interior.
| 1992-09-09
| 2016-08-31
|
[
"funct-an",
"math.FA"
] |
Alberto Bressan and Graziano Crasta
|
funct-an/9208001
|
Universal arrows to forgetful functors from categories of topological
algebra
|
We survey the present trends in theory of universal arrows to forgetful
functors from various categories of topological algebra and functional analysis
to categories of topology and topological algebra. Among them are free
topological groups, free locally convex spaces, free Banach-Lie algebras, and
much more. An accent is put on relationship of those constructions with other
areas of mathematics and their possible applications. A number of open problems
is discussed; some of them belong to universal arrow theory, and others may
hopefully become amenable to methods of this theory.
| 1992-08-20
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Vladimir G. Pestov
|
funct-an/9205003
|
Nonstandard hulls of Banach-Lie groups and algebras
|
We propose a new construction of Banach-Lie groups and algebras relying on
nonstandard analysis. A major standard application is the Local Theorem which
to certain extent reduces the problem of associating a Lie group to a given
banach-Lie algebra to a similar problem for finitely generated Lie subalgebras.
We discuss possible applications, e.g., to gauge theories.
| 1992-05-19
| 2008-02-03
|
[
"funct-an",
"math.OA"
] |
Vladimir G. Pestov
|
funct-an/9205002
|
Integral representation for a class of $C^1$-convex functionals
|
In view of the applications to the asymptotic analysis of a family of
obstacle problems, we consider a class of convex local functionals $F(u,A)$,
defined for all functions $u$ in a suitable vector valued Sobolev space and for
all open sets $A$ in ${\bf R}^n$. Sufficient conditions are given in order to
obtain an integral representation of the form $F(u,A)=\int_A f(x,u(x))\,d\mu +
\nu(A)$, where $\mu$ and $\nu$ are Borel measures and $f$ is convex in the
second variable.
| 1992-05-11
| 2008-02-03
|
[
"funct-an",
"math.FA"
] |
Gianni Dal Maso, Anneliese Defranceschi, Enrico Vitali
|
funct-an/9205001
|
A Baire Category Approach to the Bang-Bang Property
|
Aim of this paper is to develop a new technique, based on the Baire category
theorem, in order to establish the closure of reachable sets and the existence
of optimal trajectories for control systems, without the usual convexity
assumptions. The bang-bang property is proved for a new class of ``concave"
multifunctions, characterized by the existence of suitable linear selections.
The proofs rely on Lyapunov's theorem in connection with a Baire category
argument.
| 1992-05-06
| 2008-02-03
|
[
"funct-an",
"math.FA"
] |
Alberto Bressan and Benedetto Piccoli
|
gr-qc/9212016
|
String Instabilities in Black Hole Spacetimes
|
We study the emergence of string instabilities in $D$ - dimensional black
hole spacetimes (Schwarzschild and Reissner - Nordstr\o m), and De Sitter space
(in static coordinates to allow a better comparison with the black hole case).
We solve the first order string fluctuations around the center of mass motion
at spatial infinity, near the horizon and at the spacetime singularity. We find
that the time components are always well behaved in the three regions and in
the three backgrounds. The radial components are {\it unstable}: imaginary
frequencies develop in the oscillatory modes near the horizon, and the
evolution is like $(\tau-\tau_0)^{-P}$, $(P>0)$, near the spacetime
singularity, $r\to0$, where the world - sheet time $(\tau-\tau_0)\to0$, and the
proper string length grows infinitely. In the Schwarzschild black hole, the
angular components are always well - behaved, while in the Reissner - Nordstr\o
m case they develop instabilities inside the horizon, near $r\to0$ where the
repulsive effects of the charge dominate over those of the mass. In general,
whenever large enough repulsive effects in the gravitational background are
present, string instabilities develop. In De Sitter space, all the spatial
components exhibit instability. The infalling of the string to the black hole
singularity is like the motion of a particle in a potential
$\gamma(\tau-\tau_0)^{-2}$ where $\gamma$ depends on the $D$ spacetime
dimensions and string angular momentum, with $\gamma>0$ for Schwarzschild and
$\gamma<0$ for Reissner - Nordstr\o m black holes. For $(\tau-\tau_0)\to0$ the
string ends trapped by the black hole singularity.
| 1992-12-30
| 2009-10-22
|
[
"gr-qc",
"hep-th"
] |
C.O.Lousto and N. S\'anchez
|
gr-qc/9212015
|
(1+1)-Dimensional Methods for General Relativity
|
This is an article contributed to the Brill Festschrift, in honor of the 60th
birthday of Prof. D.R. Brill, which will appear in the Vol.2 of the Proceedings
of the International Symposia on Directions in General Relativity. In this
article we present the (1+1)-dimensional method for studying general relativity
of 4-dimensions. We first discuss the general formalism, and subsequently draw
attention to the algebraically special class of space-times, following the
Petrov classification. It is shown that this class of space-times can be
described by the (1+1)-dimensional Yang-Mills action interacting with matter
fields, with the spacial diffeomorphisms of the 2-surface as the gauge
symmetry. The constraint appears polynomial in part, whereas the non-polynomial
part is a non-linear sigma model type in (1+1)-dimensions. It is also shown
that the representations of $w_{\infty}$-gravity appear naturally as special
cases of this description, and we discuss briefly the $w_{\infty}$-geometry in
term of the fibre bundle.
| 1992-12-29
| 2007-05-23
|
[
"gr-qc"
] |
J.H. Yoon
|
gr-qc/9212014
|
Anisotropic and inhomogeneous cosmologies
|
This review was given at the 65th birthday meeting of D.W. Sciama, The
Renaissance of General Relativity and Cosmology, to be published by Cambridge
University Press. It presents progress in the understanding of non-standard
relativistic cosmologies during Sciama's career, organized by the areas of
application rather than the mathematical types of the models.
| 1992-12-21
| 2008-02-12
|
[
"gr-qc"
] |
M.A.H. MacCallum
|
gr-qc/9212013
|
Inhomogeneous and anisotropic cosmologies
|
This is a review of cosmological models prepared for the Pont d'Oye workshop
on the origin of structure in the universe. The classes of models are discussed
in turn, and then some of their uses are considered.
| 1992-12-21
| 2011-03-28
|
[
"gr-qc"
] |
M.A.H. MacCallum
|
gr-qc/9212012
|
Collisions of Einstein-Conformal Scalar Waves
|
A large class of solutions of the Einstein-conformal scalar equations in
D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic
conformal scalar waves and are generated from Einstein-minimally coupled scalar
spacetimes via a (generalized) Bekenstein transformation. Particular emphasis
is given to the study of the global properties and the singularity structure of
the obtained solutions. It is shown, that in the case of the absence of pure
gravitational radiation in the initial data, the formation of the final
singularity is not only generic, but is even inevitable.
| 1992-12-18
| 2016-08-17
|
[
"gr-qc"
] |
C. Klim\v{c}\'ik and P. Koln\'ik
|
gr-qc/9212011
|
A Nonlinear Model of a Quantum Minisuperspace System with Back Reaction
|
We consider the quantum evolution of the space-independent mode of a $\lambda
{\phi}^4$ theory as a minisuperspace in the space of all $\phi$. The motion of
the wave packet in the minisuperspace is then compared to the motion of a wave
packet in a larger minisuperspace consisting of the original minisuperspace
plus one space-dependent mode. By comparing the motion of the two packets we
develop criteria that tell us when the quantum evolution in the
space-independent minisuperspace gives us useful information about the true
evolution in the larger minisuperspace. These criteria serve as a toy model for
similar(but much more complex) criteria that will tell us whether or when
quantized gravitational minisuperspaces can possibly give any useful
information about quantum gravity.
| 1992-12-16
| 2011-07-19
|
[
"gr-qc"
] |
Marcos Rosenbaum, Michael P. Ryan and Sukanya Sinha
|
gr-qc/9212010
|
Black Hole Tunneling Entropy and the Spectrum of Gravity
|
The tunneling approach for entropy generation in quantum gravity is applied
to black holes. The area entropy is recovered and shown to count only a tiny
fraction of the black hole degeneracy. The latter stems from the extension of
the wave function outside the barrier. In fact the semi-classical analysis
leads to infinite degeneracy. Evaporating black holes leave then infinitely
degenerate "planckons" remnants which can neither decay into, nor be formed
from, ordinary matter in a finite time. Quantum gravity opens up at the Planck
scale into an infinite Hilbert space which is expected to provide the
ultraviolet cutoff required to render the theory finite in the sector of large
scale physics.
| 1992-12-15
| 2010-04-06
|
[
"gr-qc",
"hep-th"
] |
A. Casher and F. Englert
|
gr-qc/9212009
|
Magnetically Charged Black Holes and their Stability
|
We study magnetically charged black holes in the Einstein-Yang-Mills-Higgs
theory in the limit of infinitely strong coupling of the Higgs field. Using
mixed analytical and numerical methods we give a complete description of static
spherically symmetric black hole solutions, both abelian and nonabelian. In
particular, we find a new class of extremal nonabelian solutions. We show that
all nonabelian solutions are stable against linear radial perturbations. The
implications of our results for the semiclassical evolution of magnetically
charged black holes are discussed.
| 1992-12-14
| 2010-11-01
|
[
"gr-qc",
"hep-th"
] |
Peter C. Aichelburg and Piotr Bizon
|
gr-qc/9212007
|
Weak-Field Gravity of Revolving Circular Cosmic Strings
|
A weak-field solution of Einstein's equations is constructed. It is generated
by a circular cosmic string revolving in its plane about the centre of the
circle. (The revolution is introduced to prevent the string from collapsing.)
This solution exhibits a conical singularity, and the corresponding deficit
angle is the same as for a straight string of the same linear energy density,
irrespective of the angular velocity of the string.
| 1992-12-10
| 2009-10-22
|
[
"gr-qc"
] |
Des J. Mc Manus and Michel A. Vandyck
|
gr-qc/9212006
|
On Cosmological Isotropy, Quantum Cosmology and the Weyl Curvature
Hypothesis
|
The increasing entropy, large-scale isotropy and approximate flatness of the
universe are considered in the context of signature change, which is a
classical model of quantum tunnelling in quantum cosmology. The signature
change hypothesis implies an initial inflationary epoch, the magnetic half of
the Weyl curvature hypothesis, and a close analogue of the conformal
singularity hypothesis. Adding the electric half of the Weyl curvature
hypothesis yields, for a perfect fluid, only homogeneous and isotropic
cosmologies. In the cosmological-constant case, the unique solution is the
Vilenkin tunnelling solution, which gives a de Sitter cosmology.
| 1992-12-10
| 2010-04-06
|
[
"gr-qc"
] |
Sean A. Hayward
|
gr-qc/9212008
|
The Coherent State Representation of Quantum Fluctuations in the Early
Universe
|
Using the squeezed state formalism the coherent state representation of
quantum fluctuations in an expanding universe is derived. It is shown that this
provides a useful alternative to the Wigner function as a phase space
representation of quantum fluctuations. The quantum to classical transition of
fluctuations is naturally implemented by decohering the density matrix in this
representation. The entropy of the decohered vacua is derived. It is shown that
the decoherence process breaks the physical equivalence between vacua that
differ by a coordinate dependent phase generated by a surface term in the
Lagrangian. In particular, scale invariant power spectra are only obtained for
a special choice of surface term.
| 1992-12-10
| 2009-10-22
|
[
"gr-qc",
"astro-ph"
] |
A.L. Matacz
|
gr-qc/9212005
|
Dark Matter and Non-Newtonian Gravity From General Relativity on a
Stringy Background
|
An exact solution of Einstein's field equations for a static spherically
symmetric medium with a radially boost invariant energy-momentum tensor is
presented. In the limit of an equation of state corresponding to a distribution
of radially directed strings there is a $1/r$ correction to Newton's force law.
At large distances and small accelerations this law coincides with the
phenomenological force law invented by Milgrom in order to explain the flat
rotation curves of galaxies without introducing dark matter. The present model
explaines why the critical acceleration of Milgrom is of the same order of
magnitude as the Hubble parameter.
| 1992-12-09
| 2007-05-23
|
[
"gr-qc"
] |
Harald H. Soleng
|
gr-qc/9212002
|
Galilean Theories of Gravitation
|
A generalization of Newtonian gravitation theory is obtained by a suitable
limiting procedure from the ADM action of general relativity coupled to a
mass-point. Three particular theories are discussed and it is found that two of
them are invariant under an extended Galilei gauge group.
| 1992-12-03
| 2008-02-03
|
[
"gr-qc"
] |
R. De Pietri, L. Lusanna, M. Pauri
|
gr-qc/9212003
|
Exotic Differentiable Structures and General Relativity
|
We review recent developments in differential topology with special concern
for their possible significance to physical theories, especially general
relativity. In particular we are concerned here with the discovery of the
existence of non-standard (``fake'' or ``exotic'') differentiable structures on
topologically simple manifolds such as $S^7$, \R and $S^3\times {\bf R^1}.$
Because of the technical difficulties involved in the smooth case, we begin
with an easily understood toy example looking at the role which the choice of
complex structures plays in the formulation of two-dimensional vacuum
electrostatics. We then briefly review the mathematical formalisms involved
with differentiable structures on topological manifolds, diffeomorphisms and
their significance for physics. We summarize the important work of Milnor,
Freedman, Donaldson, and others in developing exotic differentiable structures
on well known topological manifolds. Finally, we discuss some of the geometric
implications of these results and propose some conjectures on possible physical
implications of these new manifolds which have never before been considered as
physical models.
| 1992-12-03
| 2009-10-22
|
[
"gr-qc"
] |
Carl H. Brans and Duane Randall
|
gr-qc/9212004
|
Quantum Vacuum Instability Near Rotating Stars
|
We discuss the Starobinskii-Unruh process for the Kerr black hole. We show
how this effect is related to the theory of squeezed states. We then consider a
simple model for a highly relativistic rotating star and show that the
Starobinskii-Unruh effect is absent.
| 1992-12-03
| 2009-10-22
|
[
"gr-qc"
] |
A L Matacz, A C Ottewill and P C W Davies
|
gr-qc/9212001
|
Cosmic Censorship in 2-Dimensional Dilaton Gravity
|
The global structure of 2-dimensional dilaton gravity is studied, attending
in particular to black holes and singularities. A gravitational energy is
defined and shown to be positive at spatial singularities and negative at
temporal singularities. Trapped points are defined, and it is shown that
spatial singularities are trapped and temporal singularities are not. Thus a
local form of cosmic censorship holds for positive energy. In an analogue of
gravitational collapse to a black hole, matter falling into an initially flat
space creates a spatial curvature singularity which is cloaked in a spatial or
null apparent horizon with non-decreasing energy and area.
| 1992-12-02
| 2010-04-06
|
[
"gr-qc"
] |
Sean A. Hayward
|
gr-qc/9211028
|
Thawing the Frozen Formalism: The Difference Between Observables and
What We Observe
|
In a parametrized and constrained Hamiltonian system, an observable is an
operator which commutes with all (first-class) constraints, including the
super-Hamiltonian. The problem of the frozen formalism is to explain how
dynamics is possible when all observables are constants of the motion. An
explicit model of a measurement-interaction in a parametrized Hamiltonian
system is used to elucidate the relationship between three definitions of
observables---as something one observes, as self-adjoint operators, and as
operators which commute with all of the constraints. There is no inconsistency
in the frozen formalism when the measurement process is properly understood.
The projection operator description of measurement is criticized as an
over-idealization which treats measurement as instantaneous and
non-destructive. A more careful description of measurement necessarily involves
interactions of non-vanishing duration. This is a first step towards a more
even-handed treatment of space and time in quantum mechanics. (This paper was
written for the festschrift of Dieter Brill.)
| 1992-11-25
| 2007-05-23
|
[
"gr-qc",
"hep-th"
] |
Arlen Anderson
|
gr-qc/9211027
|
Chaotic Friedmann-Robertson-Walker Cosmology
|
We show that the dynamics of a spatially closed Friedmann - Robertson -
Walker Universe conformally coupled to a real, free, massive scalar field, is
chaotic, for large enough field amplitudes. We do so by proving that this
system is integrable under the adiabatic approximation, but that the
corresponding KAM tori break up when non adiabatic terms are considered. This
finding is confirmed by numerical evaluation of the Lyapunov exponents
associated with the system, among other criteria. Chaos sets strong limitations
to our ability to predict the value of the field at the Big Crunch, from its
given value at the Big Bang. (Figures available on request)
| 1992-11-23
| 2010-04-06
|
[
"gr-qc"
] |
E. Calzetta and C. El Hasi
|
gr-qc/9211026
|
Cauchy horizon singularity without mass inflation
|
A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the
nature of the singularity along the Cauchy horizon of a charged spherically
symmetric black hole. For these solutions, conditions may prevail under which
the mass function is bounded and yet the curvature scalar
$R_{\alpha\beta\gamma\delta} R^{\alpha\beta\gamma\delta}$ diverges.
| 1992-11-20
| 2009-10-22
|
[
"gr-qc",
"astro-ph"
] |
P.R. Brady, D. Nunez and S. Sinha
|
gr-qc/9211023
|
Gravitational Waves in the Nonsymmetric Gravitational Theory
|
We prove that the flux of gravitational radiation from an isolated source in
the Nonsymmetric Gravitational Theory is identical to that found in Einstein's
General Theory of Relativity.
| 1992-11-19
| 2010-11-01
|
[
"gr-qc"
] |
N. J. Cornish, J. W. Moffat and D. C. Tatarski
|
gr-qc/9211025
|
Spin effects in the inspiral of coalescing compact binaries
|
We derive the contributions of spin-orbit and spin-spin coupling to the
gravitational radiation from coalescing binary systems of spinning compact
objects. We calculate spin effects in the symmetric, trace-free radiative
multipoles that determine the gravitational waveform, and the rate of energy
loss. Assuming a balance between energy radiated and orbital energy lost, we
determine the spin effects in the evolution of the orbital frequency and
orbital radius. Assuming that a laser interferometric gravitational observatory
can track the gravitational-wave frequency (twice the orbital frequency) as it
sweeps through its sensitive bandwidth between about 10 Hz and one kHz, we
estimate the accuracy with which the spins of the component bodies can be
determined from the gravitational-wave signal.
| 1992-11-19
| 2010-01-06
|
[
"gr-qc"
] |
Lawrence E. Kidder and Clifford M. Will (Washington University, St.
Louis) and Alan G. Wiseman (Northwestern University, Evanston)
|
gr-qc/9211024
|
Tunneling in Anisotropic Cosmological Models
|
Tunneling rate is investigated in homogenous and anisotropic cosmologies. The
calculations is done by two methods: Euclidean and Hamiltonian approaches. It
is found that the probability decreases exponentialy as anisotropy is
increased.
| 1992-11-19
| 2010-04-06
|
[
"gr-qc"
] |
R. Mansouri and M.Mohazzab (BROWN)
|
gr-qc/9211022
|
Quantum Gravity by the Complex Canonical Formulation
|
The basic features of the complex canonical formulation of general relativity
and the recent developments in the quantum gravity program based on it are
reviewed. The exposition is intended to be complementary to the review articles
available already and some original arguments are included. In particular the
conventional treatment of the Hamiltonian constraint and quantum states in the
canonical approach to quantum gravity is criticized and a new formulation is
proposed.
| 1992-11-18
| 2010-11-01
|
[
"gr-qc"
] |
Hideo Kodama
|
gr-qc/9211021
|
Dilaton Contributions to the Cosmic Gravitational Wave Background
|
We consider the cosmological amplification of a metric perturbation
propagating in a higher-dimensional Brans-Dicke background, including a non
trivial dilaton evolution. We discuss the properties of the spectral energy
density of the produced gravitons (as well as of the associated squeezing
parameter), and we show that the present observational bounds on the graviton
spectrum provide significant information on the dynamical evolution of the
early universe.
| 1992-11-17
| 2009-10-22
|
[
"gr-qc",
"hep-th"
] |
M.Gasperini and M.Giovannini
|
gr-qc/9211020
|
Superluminary Universe: A Possible Solution to the Initial Value Problem
in Cosmology
|
The spontaneous breaking of local Lorentz invariance in the early Universe,
associated with a first order phase transition at a critical time $t_c$,
generates a large increase in the speed of light and a superluminary
communication of information occurs, allowing all regions in the Universe to be
causally connected. This solves the horizon problem, leads to a mechanism of
monopole suppression in cosmology and can resolve the flatness problem. After
the critical time $t_c$, local Lorentz (and diffeomorphism) invariance is
restored and light travels at its presently measured speed. The kinematical and
dynamical aspects of the generation of quantum fluctuations in the
superluminary Universe are investigated. A scale invariant prediction for the
fluctuation density amplitude is obtained.
| 1992-11-16
| 2008-11-26
|
[
"gr-qc",
"astro-ph",
"hep-th"
] |
J. W. Moffat
|
gr-qc/9211019
|
What can we learn from the study of non-perturbative quantum general
relativity?
|
I attempt to answer the question of the title by giving an annotated list of
the major results achieved, over the last six years, in the program to
construct quantum general relativity using the Ashtekar variables and the loop
representation. A summary of the key open problems is also included. Also
included are expositions of several new results including the construction of
spatially diffeomorphism invariant observables constructed by coupling general
relativity to matter fields.
| 1992-11-15
| 2007-05-23
|
[
"gr-qc"
] |
Lee Smolin
|
gr-qc/9211018
|
Generalized Fierz Identities and the Superselection Rule for Geometric
Multispinors
|
The inverse problem, to reconstruct the general multivector wave function
from the observable quadratic densities, is solved for 3D geometric algebra. It
is found that operators which are applied to the right side of the wave
function must be considered, and the standard Fierz identities do not
necessarily hold except in restricted situations, corresponding to the
spin-isospin superselection rule. The Greider idempotent and Hestenes
quaterionic spinors are included as extreme cases of a single superselection
parameter.
| 1992-11-14
| 2009-09-25
|
[
"gr-qc",
"hep-th"
] |
William M. Pezzaglia Jr. (Physics, Santa Clara University)
|
gr-qc/9211016
|
Vacuum Polarisation and the Black Hole Singularity
|
In order to investigate the effects of vacuum polarisation on mass inflation
singularities, we study a simple toy model of a charged black hole with cross
flowing radial null dust which is homogeneous in the black hole interior. In
the region $r^2 \ll e^2$ we find an approximate analytic solution to the
classical field equations. The renormalized stress-energy tensor is evaluated
on this background and we find the vacuum polarisation backreaction corrections
to the mass function $m(r)$. Asymptotic analysis of the semiclassical mass
function shows that the mass inflation singularity is much stronger in the
presence of vacuum polarisation than in the classical case.
| 1992-11-13
| 2010-04-06
|
[
"gr-qc"
] |
W. G. Anderson, P. R. Brady, and R. Camporesi
|
gr-qc/9211017
|
The Relation between Physical and Gravitational Geometry
|
The appearance of two geometries in one and the same gravitational theory is
familiar. Usually, as in the Brans-Dicke theory or in string theory, these are
conformally related Riemannian geometries. Is this the most general relation
between the two geometries allowed by physics ? We study this question by
supposing that the physical geometry on which matter dynamics take place could
be Finslerian rather than just Riemannian. An appeal to the weak equivalence
principle and causality then leads us the conclusion that the Finsler geometry
has to reduce to a Riemann geometry whose metric - the physical metric - is
related to the gravitational metric by a generalization of the conformal
transformation.
| 1992-11-13
| 2011-07-18
|
[
"gr-qc",
"astro-ph",
"hep-th"
] |
Jacob D. Bekenstein (University of California at Santa Barbara and
Hebrew University of Jerusalem)
|
gr-qc/9211015
|
Discrete Symmetry, Non-Commutative Geometry and Gravity
|
We describe the geomety of a set of scalar fields coupled to gravity. We
consider the formalism of a differential Z_2-graded algebra of $2\times 2$
matrices whose elements are differential forms on space-time. The connection
and the vierbeins are extended to incorporate additional scalar and vector
fields. The resulting action describes two universes coupled in a non-minimal
way to a set of scalar fields. This picture is slightly different from the
description of general relativity in the framework of non-commutative geomety.
| 1992-11-10
| 2007-05-23
|
[
"gr-qc",
"hep-th"
] |
N. Mohammedi
|
gr-qc/9211014
|
Unification of Gravity and Yang-Mills Theory in (2+1)-Dimensions
|
A gauge and diffeomorphism invariant theory in (2+1)-dimensions is presented
in both first and second order Lagrangian form as well as in a Hamiltonian
form. For gauge group $SO(1,2)$, the theory is shown to describe ordinary
Einstein gravity with a cosmological constant. With gauge group
$G^{tot}=SO(1,2)\otimes G^{YM}$, it is shown that the equations of motion for
the $G^{YM}$ fields are the Yang-Mills equations. It is also shown that for
weak $G^{YM}$ Yang-Mills fields, this theory agrees with the conventional
Einstein-Yang-Mills theory to lowest order in Yang-Mills fields. Explicit
static and rotation symmetric solutions to the Einstein-Maxwell theory are
studied both for the conventional coupling and for this unified theory. In the
electric solution to the unified theory, point charges are not allowed, the
charges must have spatial extensions.
| 1992-11-10
| 2009-10-22
|
[
"gr-qc",
"hep-th"
] |
Peter Peldan
|
gr-qc/9211012
|
Inflating Lorentzian Wormholes
|
It has been speculated that Lorentzian wormholes of the Morris- Thorne type
might be allowed by the laws of physics at submicroscopic, e.g. Planck, scales
and that a sufficiently advanced civilization might be able to enlarge them to
classical size. The purpose of this paper is to explore the possibility that
inflation might provide a natural mechanism for the enlargement of such
wormholes to macroscopic size. A new classical metric is presented for a
Lorentzian wormhole which is imbedded in a flat deSitter space. It is shown
that the throat and proper length of the wormhole inflate. The resulting
properties and stress-energy tensor associated with this metric are discussed.
| 1992-11-09
| 2009-10-22
|
[
"gr-qc"
] |
Thomas A. Roman
|
gr-qc/9211013
|
Gauge Formulation of the Spinning Black Hole in (2+1)-Dimensional
Anti-de Sitter Space
|
We compute the group element of SO(2,2) associated with the spinning black
hole found by Ba\~nados, Teitelboim and Zanelli in (2+1)-dimensional anti-de
Sitter space-time. We show that their metric is built with SO(2,2) gauge
invariant quantities and satisfies Einstein's equations with negative
cosmological constant everywhere except at $r=0$. Moreover, although the metric
is singular on the horizons, the group element is continuous and possesses a
kink there.
| 1992-11-09
| 2009-10-22
|
[
"gr-qc",
"hep-th"
] |
Daniel Cangemi, Martin Leblanc and Robert B. Mann
|
gr-qc/9211011
|
Weak-Field Gravity of Circular Cosmic Strings
|
A weak-field solution of Einstein's equations is constructed. It is generated
by a circular cosmic string externally supported against collapse. The solution
exhibits a conical singularity, and the corresponding deficit angle is the same
as for a straight string of the same linear energy density. This confirms the
deficit-angle assumption made in the Frolov-Israel-Unruh derivation of the
metric describing a string loop at a moment of time symmetry.
| 1992-11-09
| 2009-10-22
|
[
"gr-qc"
] |
Shane J. Hughes, Des J. Mc Manus, and Michel A. Vandyck
|
gr-qc/9211010
|
Gauge (In)variance, Mass and Parity in D=3 Revisited
|
We analyze the degree of equivalence between abelian topologically massive,
gauge-invariant, vector or tensor parity doublets and their explicitly massive,
non-gauge, counterparts. We establish equivalence of field equations by
exploiting a generalized Stueckelberg invariance of the gauge systems. Although
the respective excitation spectra and induced source-source interactions are
essentially identical, there are also differences, most dramatic being those
between the Einstein limits of the interactions in the tensor case: the
doublets avoid the discontinuity (well-known from D=4) exhibited by Pauli-Fierz
theory.
| 1992-11-06
| 2009-11-19
|
[
"gr-qc"
] |
S. Deser
|
gr-qc/9211008
|
Gauge Field Back-reaction on a Black Hole
|
The order $\hbar$ fluctuations of gauge fields in the vicinity of a blackhole
can create a repulsive antigravity region extending out beyond the renormalized
Schwarzschild horizon. If the strength of this repulsive force increases as
higher orders in the back-reaction are included, the formation of a
wormhole-like object could occur.
| 1992-11-05
| 2009-10-22
|
[
"gr-qc",
"astro-ph"
] |
David Hochberg and Thomas W. Kephart
|
gr-qc/9211009
|
Positivity of Entropy in the Semi-Classical Theory of Black Holes and
Radiation
|
Quantum stress-energy tensors of fields renormalized on a Schwarzschild
background violate the classical energy conditions near the black hole.
Nevertheless, the associated equilibrium thermodynamical entropy $\Delta S$ by
which such fields augment the usual black hole entropy is found to be positive.
More precisely, the derivative of $\Delta S$ with respect to radius, at fixed
black hole mass, is found to vanish at the horizon for {\it all} regular
renormalized stress-energy quantum tensors. For the cases of conformal scalar
fields and U(1) gauge fields, the corresponding second derivative is positive,
indicating that $\Delta S$ has a local minimum there. Explicit calculation
shows that indeed $\Delta S$ increases monotonically for increasing radius and
is positive. (The same conclusions hold for a massless spin 1/2 field, but the
accuracy of the stress-energy tensor we employ has not been confirmed, in
contrast to the scalar and vector cases). None of these results would hold if
the back-reaction of the radiation on the spacetime geometry were ignored;
consequently, one must regard $\Delta S$ as arising from both the radiation
fields and their effects on the gravitational field. The back-reaction, no
matter how "small",
| 1992-11-05
| 2009-12-30
|
[
"gr-qc"
] |
David Hochberg, Thomas Kephart and James W. York
|
gr-qc/9211006
|
Wormhole Cosmology and the Horizon Problem
|
We construct an explicit class of dynamic lorentzian wormholes connecting
Friedmann-Robertson-Walker (FRW) spacetimes. These wormholes can allow two-way
transmission of signals between spatially separated regions of spacetime and
could permit such regions to come into thermal contact. The cosmology of a
network of early Universe wormholes is discussed.
| 1992-11-04
| 2009-10-22
|
[
"gr-qc",
"hep-th"
] |
David Hochberg and Thomas W. Kephart
|
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