1,978 research outputs found
Aspects of Noncommutative Scalar/Tensor Duality
We study the noncommutative massless Kalb-Ramond gauge field coupled to a
dynamical U(1) gauge field in the adjoint representation together with a
compensating vector field. We derive the Seiberg-Witten map and obtain the
corresponding mapped action to first order in . The (emergent) gravity
structure found in other situations is not present here. The off-shell dual
scalar theory is derived and it does not coincide with the Seiberg-Witten
mapped scalar theory. Dispersion relations are also discussed. The p-form
generalization of the Seiberg-Witten map to order is also derived.Comment: 7 pages, typos corrected, a footnote removed and a sentence added in
the tex
Skolem Functions for Factored Formulas
Given a propositional formula F(x,y), a Skolem function for x is a function
\Psi(y), such that substituting \Psi(y) for x in F gives a formula semantically
equivalent to \exists F. Automatically generating Skolem functions is of
significant interest in several applications including certified QBF solving,
finding strategies of players in games, synthesising circuits and bit-vector
programs from specifications, disjunctive decomposition of sequential circuits
etc. In many such applications, F is given as a conjunction of factors, each of
which depends on a small subset of variables. Existing algorithms for Skolem
function generation ignore any such factored form and treat F as a monolithic
function. This presents scalability hurdles in medium to large problem
instances. In this paper, we argue that exploiting the factored form of F can
give significant performance improvements in practice when computing Skolem
functions. We present a new CEGAR style algorithm for generating Skolem
functions from factored propositional formulas. In contrast to earlier work,
our algorithm neither requires a proof of QBF satisfiability nor uses
composition of monolithic conjunctions of factors. We show experimentally that
our algorithm generates smaller Skolem functions and outperforms
state-of-the-art approaches on several large benchmarks.Comment: Full version of FMCAD 2015 conference publicatio
Detection of gravitational-wave bursts with chirplet-like template families
Gravitational Wave (GW) burst detection algorithms typically rely on the
hypothesis that the burst signal is "locally stationary", that is it changes
slowly with frequency. Under this assumption, the signal can be decomposed into
a small number of wavelets with constant frequency. This justifies the use of a
family of sine-Gaussian templates in the Omega pipeline, one of the algorithms
used in LIGO-Virgo burst searches. However there are plausible scenarios where
the burst frequency evolves rapidly, such as in the merger phase of a binary
black hole and/or neutron star coalescence. In those cases, the local
stationarity of sine-Gaussians induces performance losses, due to the mismatch
between the template and the actual signal. We propose an extension of the
Omega pipeline based on chirplet-like templates. Chirplets incorporate an
additional parameter, the chirp rate, to control the frequency variation. In
this paper, we show that the Omega pipeline can easily be extended to include a
chirplet template bank. We illustrate the method on a simulated data set, with
a family of phenomenological binary black-hole coalescence waveforms embedded
into Gaussian LIGO/Virgo-like noise. Chirplet-like templates result in an
enhancement of the measured signal-to-noise ratio.Comment: 8 pages, 6 figures. Submitted to Class. Quantum Grav. Special issue:
Proceedings of GWDAW-14, Rome (Italy), 2010; fixed several minor issue
Indian Medicinal Mushrooms as a Source of Antioxidant and Antitumor Agents
Medicinal mushrooms occurring in South India namely Ganoderma lucidum, Phellinus rimosus, Pleurotus florida and Pleurotus pulmonaris possessed profound antioxidant and antitumor activities. This indicated that these mushrooms would be valuable sources of antioxidant and antitumor compounds. Investigations also revealed that they had significant antimutagenic and anticarcinogenic activities. Thus, Indian medicinal mushrooms are potential sources of antioxidant and anticancer compounds. However, intensive and extensive investigations are needed to exploit their valuable therapeutic use
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