428 research outputs found
The Nonlinear Multiplet Revisited
Using a reformulation of the nonlinear multiplet as a gauge multiplet, we
discuss its dynamics. We show that the nonlinear ``duality'' that appears to
relate the model to a conventional -model introduces a new sector into
the theory.Comment: 11 pages, ITP-SB-94-23, USITP-94-1
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CP Violation at BaBar
Several new and updated BABAR measurements of sin 2{beta} are presented, together with the latest constraints on the Unitarity Triangle angles {alpha} and {gamma}. The higher statistics now available allow more sophisticated analysis techniques, such as time-dependent Dalitz plot fitting. Combined world-average results place tight constraints on the Unitarity Triangle. There is good agreement among the measurements and with the unitarity of the CKM matrix. This represents an impressive verification of the Standard Model description of the quark-flavor sector and of CP violation
State Sum Models and Simplicial Cohomology
We study a class of subdivision invariant lattice models based on the gauge
group , with particular emphasis on the four dimensional example. This
model is based upon the assignment of field variables to both the - and
-dimensional simplices of the simplicial complex. The property of
subdivision invariance is achieved when the coupling parameter is quantized and
the field configurations are restricted to satisfy a type of mod- flatness
condition. By explicit computation of the partition function for the manifold
, we establish that the theory has a quantum Hilbert space
which differs from the classical one.Comment: 28 pages, Latex, ITFA-94-13, (Expanded version with two new sections
Conformal Field Theory Interpretation of Black Hole Quasi-normal Modes
We obtain exact expressions for the quasi-normal modes of various spin for
the BTZ black hole. These modes determine the relaxation time of black hole
perturbations. Exact agreement is found between the quasi-normal frequencies
and the location of the poles of the retarded correlation function of the
corresponding perturbations in the dual conformal field theory. This then
provides a new quantitative test of the AdS/CFT correspondence.Comment: 4 pages, RevTeX, references adde
A Closed Contour of Integration in Regge Calculus
The analytic structure of the Regge action on a cone in dimensions over a
boundary of arbitrary topology is determined in simplicial minisuperspace. The
minisuperspace is defined by the assignment of a single internal edge length to
all 1-simplices emanating from the cone vertex, and a single boundary edge
length to all 1-simplices lying on the boundary. The Regge action is analyzed
in the space of complex edge lengths, and it is shown that there are three
finite branch points in this complex plane. A closed contour of integration
encircling the branch points is shown to yield a convergent real wave function.
This closed contour can be deformed to a steepest descent contour for all sizes
of the bounding universe. In general, the contour yields an oscillating wave
function for universes of size greater than a critical value which depends on
the topology of the bounding universe. For values less than the critical value
the wave function exhibits exponential behaviour. It is shown that the critical
value is positive for spherical topology in arbitrary dimensions. In three
dimensions we compute the critical value for a boundary universe of arbitrary
genus, while in four and five dimensions we study examples of product manifolds
and connected sums.Comment: 16 pages, Latex, To appear in Gen. Rel. Gra
On the influence of the cosmological constant on gravitational lensing in small systems
The cosmological constant Lambda affects gravitational lensing phenomena. The
contribution of Lambda to the observable angular positions of multiple images
and to their amplification and time delay is here computed through a study in
the weak deflection limit of the equations of motion in the Schwarzschild-de
Sitter metric. Due to Lambda the unresolved images are slightly demagnified,
the radius of the Einstein ring decreases and the time delay increases. The
effect is however negligible for near lenses. In the case of null cosmological
constant, we provide some updated results on lensing by a Schwarzschild black
hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation,
references added, results unchanged, in press on PR
Relaxation in Conformal Field Theory, Hawking-Page Transition, and Quasinormal/Normal Modes
We study the process of relaxation back to thermal equilibrium in
-dimensional conformal field theory at finite temperature. When the size
of the system is much larger than the inverse temperature, perturbations decay
exponentially with time. On the other hand, when the inverse temperature is
large, the relaxation is oscillatory with characteristic period set by the size
of the system. We then analyse the intermediate regime in two specific models,
namely free fermions, and a strongly coupled large conformal field
theory which is dual to string theory on -dimensional anti-de Sitter
spacetime. In the latter case, there is a sharp transition between the two
regimes in the limit, which is a manifestation of the
gravitational Hawking-Page phase transition. In particular, we establish a
direct connection between quasinormal and normal modes of the gravity system,
and the decaying and oscillating behaviour of the conformal field theory.Comment: 10 pages, latex, no figure
Gravitational collapse in 2+1 dimensional AdS spacetime
We present results of numerical simulations of the formation of black holes
from the gravitational collapse of a massless, minimally-coupled scalar field
in 2+1 dimensional, axially-symmetric, anti de-Sitter (AdS) spacetime. The
geometry exterior to the event horizon approaches the BTZ solution, showing no
evidence of scalar `hair'. To study the interior structure we implement a
variant of black-hole excision, which we call singularity excision. We find
that interior to the event horizon a strong, spacelike curvature singularity
develops. We study the critical behavior at the threshold of black hole
formation, and find a continuously self-similar solution and corresponding
mass-scaling exponent of approximately 1.2. The critical solution is universal
to within a phase that is related to the angle deficit of the spacetime.Comment: 31 pages, 20 figures, LaTeX. Replaced with version to be published in
Phys. Rev.
Classical and Quantized Tensionless Strings
{}From the ordinary tensile string we derive a geometric action for the
tensionless () string and discuss its symmetries and field equations. The
Weyl symmetry of the usual string is shown to be replaced by a global
space-time conformal symmetry in the limit. We present the explicit
expressions for the generators of this group in the light-cone gauge. Using
these, we quantize the theory in an operator form and require the conformal
symmetry to remain a symmetry of the quantum theory. Modulo details concerning
zero-modes that are discussed in the paper, this leads to the stringent
restriction that the physical states should be singlets under space-time
diffeomorphisms, hinting at a topological theory. We present the details of the
calculation that leads to this conclusion.Comment: 34 pages, Latex, USITP 93-1
Black hole collision with a scalar particle in three dimensional anti-de Sitter spacetime
We study the collision between a BTZ black hole and a test particle coupled
to a scalar field. We compute the power spectrum, the energy radiated and the
plunging waveforms for this process. We show that for late times the signal is
dominated by the quasinormal ringing. In terms of the AdS/CFT correspondence
the bulk gravity process maps into a thermal state, an expanding bubble and
gauge particles decaying into bosons of the associated operator. These latter
thermalize in a timescale predicted by the bulk theory.Comment: 5 pages, 3 figures;minor improvements; references adde
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