2,311 research outputs found
Diffeomorphism Cohomology in Beltrami Parametrization II : The 1-Forms
We study the 1-form diffeomorphism cohomologies within a local conformal
Lagrangian Field Theory model built on a two dimensional Riemann surface with
no boundary. We consider the case of scalar matter fields and the complex
structure is parametrized by Beltrami differential. The analysis is first
performed at the Classical level, and then we improve the quantum extension,
introducing the current in the Lagrangian dynamics, coupled to external source
fields. We show that the anomalies which spoil the current conservations take
origin from the holomorphy region of the external fields, and only the
differential spin 1 and 2 currents (as well their c.c) could be anomalous.Comment: 39 pages,CPT-94/P.3072,LaTe
Improved Epstein-Glaser Renormalization II. Lorentz invariant framework
The Epstein--Glaser type T-subtraction introduced by one of the authors in a
previous paper is extended to the Lorentz invariant framework. The advantage of
using our subtraction instead of Epstein and Glaser's standard W-subtraction
method is especially important when working in Minkowski space, as then the
counterterms necessary to keep Lorentz invariance are simplified. We show how
T-renormalization of primitive diagrams in the Lorentz invariant framework
directly relates to causal Riesz distributions. A covariant subtraction rule in
momentum space is found, sharply improving upon the BPHZL method for massless
theories.Comment: LaTeX, 15 pages, no figure. Version to be published in J. Math. Phys.
(Section 7 on the Massive Case and some references have been withdrawn). To
the Memory of Laurent Schwart
On a Classification of Irreducible Almost Commutative Geometries
We classify all irreducible, almost commutative geometries whose spectral
action is dynamically non-degenerate. Heavy use is made of Krajewski's
diagrammatic language. The motivation for our definition of dynamical
non-degeneracy stems from particle physics where the fermion masses are
non-degenerate.Comment: 47 pages, 9 figure
Extended hierarchical search (EHS) algorithm for detection of gravitational waves from inspiraling compact binaries
Pattern matching techniques like matched filtering will be used for online
extraction of gravitational wave signals buried inside detector noise. This
involves cross correlating the detector output with hundreds of thousands of
templates spanning a multi-dimensional parameter space, which is very expensive
computationally. A faster implementation algorithm was devised by Mohanty and
Dhurandhar [1996] using a hierarchy of templates over the mass parameters,
which speeded up the procedure by about 25 to 30 times. We show that a further
reduction in computational cost is possible if we extend the hierarchy paradigm
to an extra parameter, namely, the time of arrival of the signal. In the first
stage, the chirp waveform is cut-off at a relatively low frequency allowing the
data to be coarsely sampled leading to cost saving in performing the FFTs. This
is possible because most of the signal power is at low frequencies, and
therefore the advantage due to hierarchy over masses is not compromised.
Results are obtained for spin-less templates up to the second post-Newtonian
(2PN) order for a single detector with LIGO I noise power spectral density. We
estimate that the gain in computational cost over a flat search is about 100.Comment: 6 pages, 6 EPS figures, uses CQG style iopart.cl
Plans for the LIGOâTAMA joint search for gravitational wave bursts
We describe the plans for a joint search for unmodelled gravitational wave bursts being carried out by the LIGO and TAMA Collaborations using data collected during FebruaryâApril 2003. We take a conservative approach to detection, requiring candidate gravitational wave bursts to be seen in coincidence by all four interferometers. We focus on some of the complications of performing this coincidence analysis, in particular the effects of the different alignments and noise spectra of the interferometers
The role of complex structures in w-symmetry
In a symplectic framework, the infinitesimal action of symplectomorphisms
together with suitable reparametrizations of the two dimensional complex base
space generate some type of W-algebras. It turns out that complex structures
parametrized by Beltrami differentials play an important role in this context.
The construction parallels very closely two dimensional Lagrangian conformal
models where Beltrami differentials are fundamental.Comment: LaTex, 34 pages, no figures, to be published in Nucl. Phys.
The Polyakov action on the supertorus
A consistent method for obtaining a well-defined Polyakov action on the
supertorus is presented. This method uses the covariantization of derivative
operators and enables us to construct a Polyakov action which is globally
defined.Comment: 15 pages LaTe
Large Chiral Diffeomorphisms on Riemann Surfaces and W-algebras
The diffeomorphism action lifted on truncated (chiral) Taylor expansion of a
complex scalar field over a Riemann surface is presented in the paper under the
name of large diffeomorphisms. After an heuristic approach, we show how a
linear truncation in the Taylor expansion can generate an algebra of symmetry
characterized by some structure functions. Such a linear truncation is
explicitly realized by introducing the notion of Forsyth frame over the Riemann
surface with the help of a conformally covariant algebraic differential
equation. The large chiral diffeomorphism action is then implemented through a
B.R.S. formulation (for a given order of truncation) leading to a more
algebraic set up. In this context the ghost fields behave as holomorphically
covariant jets. Subsequently, the link with the so called W-algebras is made
explicit once the ghost parameters are turned from jets into tensorial ghost
ones. We give a general solution with the help of the structure functions
pertaining to all the possible truncations lower or equal to the given order.
This provides another contribution to the relationship between KdV flows and
W-diffeomorphimsComment: LaTeX file, 31 pages, no figure. Version to appear in J. Math. Phys.
Work partly supported by Region PACA and INF
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