854 research outputs found
On holography from redux, renormalization group flows and -functions
Extremal black branes upon compactification in the near horizon throat region
are known to give rise to dilaton-gravity-matter theories. Away from
the throat region, the background has nontrivial profile. We interpret this as
holographic renormalization group flow in the 2-dim dilaton-gravity-matter
theories arising from dimensional reduction of the higher dimensional theories
here. The null energy conditions allow us to formulate a holographic c-function
in terms of the 2-dim dilaton for which we argue a c-theorem subject to
appropriate boundary conditions which amount to restrictions on the ultraviolet
theories containing these extremal branes. At the infrared fixed point,
the c-function becomes the extremal black brane entropy. We discuss the
behaviour of this inherited c-function in various explicit examples, in
particular compactified nonconformal branes, and compare it with other
discussions of holographic c-functions. We also adapt the holographic
renormalization group formulated in terms of radial Hamiltonian flow to 2-dim
dilaton-gravity-scalar theories, which while not Wilsonian, gives qualitative
insight into the flow equations and -functions.Comment: Latex, 40pgs incl appendices; v2: minor tweaks, figure added; v3:
minor clarifications added, matches version to be publishe
Hyperscaling violation and the shear diffusion constant
We consider holographic theories in bulk -dimensions with Lifshitz and
hyperscaling violating exponents at finite temperature. By studying
shear gravitational modes in the near-horizon region given certain
self-consistent approximations, we obtain the corresponding shear diffusion
constant on an appropriately defined stretched horizon, adapting the analysis
of Kovtun, Son and Starinets. For generic exponents with , we
find that the diffusion constant has power law scaling with the temperature,
motivating us to guess a universal relation for the viscosity bound. When the
exponents satisfy , we find logarithmic behaviour. This relation
is equivalent to where is the effective
boundary spatial dimension (and the actual spatial dimension). It is
satisfied by the exponents in hyperscaling violating theories arising from null
reductions of highly boosted black branes, and we comment on the corresponding
analysis in that context.Comment: Latex, 17pgs, v3: clarifications added on z<2+d_{eff} and standard
quantization, to be publishe
Stock Market Integration and Volatility Spillover:India and its Major Asian Counterparts
Return and volatility spillover among Indian stock market with that of 12 other developed and emerging Asian countries over a period from November 1997 to April 2008 is studied. Daily opening and closing prices of all major equity indices from the sample countries are examined by applying the GARCH model [Engle (1982) and Bollerslev (1986)] to explore the possibility of stock market integration and volatility spillover among India and its major Asian counterparties. Apart from different degrees of correlations, both in terms of return and squared return series, among Indian stock market with that of other Asian countries, the contemporaneous intraday return spillover among India and almost all the sample countries are found to be positively significant and bi-directional. More specifically, Hong Kong, Korea, Singapore and Thailand are found to be the four Asian markets from where there is a significant flow of information in India. Similarly, among others, stock markets in Pakistan and Sri Lanka are found to be strongly influenced by movements in Indian market. Though most of the information gets transmitted among the markets without much delay, some amount of information still remains and can successfully transmit as soon as the market opens in the next day.Asian stock markets; Integration; Information spillover; GARCH model
Symmetry breaking perturbations and strange attractors
The asymmetrically forced, damped Duffing oscillator is introduced as a
prototype model for analyzing the homoclinic tangle of symmetric dissipative
systems with \textit{symmetry breaking} disturbances. Even a slight fixed
asymmetry in the perturbation may cause a substantial change in the asymptotic
behavior of the system, e.g. transitions from two sided to one sided strange
attractors as the other parameters are varied. Moreover, slight asymmetries may
cause substantial asymmetries in the relative size of the basins of attraction
of the unforced nearly symmetric attracting regions. These changes seems to be
associated with homoclinic bifurcations. Numerical evidence indicates that
\textit{strange attractors} appear near curves corresponding to specific
secondary homoclinic bifurcations. These curves are found using analytical
perturbational tools
Thermal stresses in functionally graded hollow sphere due to non-uniform internal heat generation
In this article, the thermal stresses in a hollow thick sphere of functionally graded material subjected to non-uniform internal heat generation are obtained as a function of radius to an exact solution by using the theory of elasticity. Material properties and heat generation are assumed as a function of radius of sphere and Poissonâs ratio as constant. The distribution of thermal stresses for different values of the powers of the module of elasticity and varying power law index of heat generation is studied. The results are illustrated numerically and graphically
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