Mod.Phys.Lett.A21:1851-1863,2006 We study noncommutative field theories, which are inherently nonlocal, using
a Poincar\'e-invariant regularisation scheme which yields an effective,
nonlocal theory ...for energies below a cut-off scale. After discussing the
general features and the peculiar advantages of this regularisation scheme for
theories defined in noncommutative spaces, we focus our attention onto the
particular case when the noncommutativity parameter is inversely proportional
to the square of the cut-off, via a dimensionless parameter $\eta$. We work out
the perturbative corrections at one-loop order for a scalar theory with quartic
interactions, where the signature of noncommutativity appears in
$\eta$-dependent terms. The implications of this approach, which avoids the
problems related to UV-IR mixing, are discussed from the perspective of the
Wilson renormalisation program. Finally, we remark about the generality of the
method, arguing that it may lead to phenomenologically relevant predictions,
when applied to realistic field theories.
The authors analyze a single processor multithreaded architecture using stochastic timed Petri net (STPN) model to study the effects of various parameters such as memory latency and thread runlength, ...on processor utilization. They first perform a simple analysis of the basic model with constant values for the parameters. This is followed by an extension with stochastic parameters. A detailed simulation study is conducted to validate the analysis. While earlier researchers established that an increase in the number of threads results in increased processor utilization, their results, on the other hand, indicate that average runlength and effective memory latency have stronger impact on processor utilization than the number of threads.< >
Nucl.Phys. B655 (2003) 300-312 We formulate the $O(3) \s-$ model on fuzzy sphere and construct the Hopf
term. We show that the field can be expanded in terms of the ladder operators
of ...Holstein-Primakoff realisation of SU(2) algebra and the corresponding basis
set can be classified into different topological sectors by the magnetic
quantum numbers. We obtain topological charge $Q$ and show that $-2j\le Q
\le2j$. We also construct BPS solitons. Using the covariantly conserved
current, we construct the Hopf term and show that its value is $Q^2$ as in the
commutative case. We also point out the interesting relation of physical space
to deformed SU(2) algebra.
In a previous paper 1, we studied the \(\eta'\) mass and formulated its chirally symmetric coupling to fermions which induces electric dipole moment (EDM). Here we calculate the EDM to one-loop. It ...is finite, having no ultraviolet divergence while its infrared divergence is canceled by soft photon emission processes \emph{exactly} as for \(\theta=0\). The coupling does not lead to new divergences (not present for \(\sin\theta=0\)) in soft photon processes either. Furthermore, as it was argued previously 1, the EDM vanishes if suitable mixed quantum states are used. This means that in a quantum theory based on such mixed states, a strong bound on EDM will not necessarily lead to a strong bound such as \(|\sin \theta|\lesssim 10^{-11}\) . This fact eliminates the need to fine-tune \(\theta\) or for the axion field.
The study of BTZ blackhole physics and the cosmological horizon of 3D de Sitter spaces are carried out in unified way using the connections to the Chern Simons theory on three manifolds with ...boundary. The relations to CFT on the boundary is exploited to construct exact partition functions and obtain logarithmic corrections to Bekenstein formula in the asymptotic regime. Comments are made on the dS/CFT correspondence frising from these studies.
Knot Solitons Govindarajan, T R
11/1998
Journal Article
Odprti dostop
Mod.Phys.Lett. A13 (1998) 3179-3184 The existence of ring-like and knotted solitons in O(3) non-linear sigma
model is analysed. The role of isotopy of knots/links in classifying such
solitons is ...pointed out. Appearance of torus knot solitons is seen.
Phys.Rev.D80:025014,2009 In this paper we study the deformed statistics and oscillator algebras of
quantum fields defined in $\kappa$-Minkowski spacetime. The twisted flip
operator obtained from the ...twist associated with the star product requires an
enlargement of the Poincar\'e algebra to include the dilatation generators.
Here we propose a novel notion of a fully covariant flip operator and show that
to the first order in the deformation parameter it can be expressed completely
in terms of the Poincar\'e generators alone. The $R$-matrices corresponding to
the twisted and the covariant flip operators are compared up to first order in
the deformation parameter and they are shown to be different. We also construct
the deformed algebra of the creation and annihilation operators that arise in
the mode expansion of a scalar field in $\kappa$-Minkowski spacetime. We obtain
a large class of such new deformed algebras which, for certain choice of
realizations, reduce to results known in the literature.
We show that the non-commutative \(CP^1\) model coupled with Hopf term in 3 dimensions is equivalent to an interacting spin-\(s\) theory where the spin \(s\) of the dual theory is related to the ...coefficient of the Hopf term. We use the Seiberg-Witten map in studying this non-commutative duality equivalence, keeping terms to order \(\theta\) and show that the spin of the dual theory do not get any \(\theta\) dependant corrections. The map between current correlators show that topological index of the solitons in the non-commutative \(CP^1\) model is unaffected by \(\theta\) where as the Noether charge of the corresponding dual particle do get a \(\theta\) dependence. We also show that this dual theory smoothly goes to the limit \(\theta\to 0\) giving dual theory in the commutative plane.
Class.Quant.Grav. 18 (2001) 265-276 A novel method, based on superpotentials is proposed for obtaining the
quasi-normal modes of anti-de Sitter black holes. This is inspired by the case
of the ...three-dimensional BTZ black hole, where the quasi-normal modes can be
obtained exactly and are proportional to the surface gravity. Using this
approach, the quasi-normal modes of the five dimensional Schwarzschild
anti-deSitter black hole are computed numerically. The modes again seem to be
proportional to the surface gravity for very small and very large black holes.
They reflect the well-known instability of small black holes in anti-deSitter
space.
