State-space Geometry, Statistical Fluctuations and Black Holes in String Theory

We study the state-space geometry of various extremal and nonextremal black holes in string theory. From the notion of the intrinsic geometry, we offer a new perspective of black hole vacuum fluctuations. For a given black hole entropy, we explicate the intrinsic state-space geometric meaning of the statistical fluctuations, local and global stability conditions and long range statistical correlations. We provide a set of physical motivations pertaining to the extremal and nonextremal black holes, \textit{viz.}, the meaning of the chemical geometry and physics of correlation. We illustrate the state-space configurations for general charge extremal black holes. In sequel, we extend our analysis for various possible charge and anticharge nonextremal black holes. From the perspective of statistical fluctuation theory, we offer general remarks, future directions and open issues towards the intrinsic geometric understanding of the vacuum fluctuations and black holes in string theory. Keywords: Intrinsic Geometry; String Theory; Physics of black holes; Classical black holes; Quantum aspects of black holes, evaporation, thermodynamics; Higher-dimensional black holes, black strings, and related objects; Statistical Fluctuation; Flow Instability. PACS: 02.40.Ky; 11.25.-w; 04.70.-s; 04.70.Bw; 04.70.Dy; 04.50.Gh; 5.40.-a; 47.29.KyComment: 28 pages. arXiv admin note: substantial text overlap with arXiv:1102.239

Chaos and predictability of the Indian summer monsoon

Predictability of the Indian summer monsoon is investigated by conducting three multiyear integrations with the Geophysical Fluid Dynamics Laboratory's climate model. The mean monsoon simulated by the model is realistic. It is shown that a significant fraction of the interannual variance of the simulated Indian summer monsoon may be due to internal dynamics. It is discovered that the tropical atmosphere is capable of sustaining a quasi-biennial oscillation (QBO) accounting for most of the internal low frequency variability. It is also shown that neither air-sea interaction nor surface hydrology feedback is essential for the QBO of the model atmosphere. That such a QBO can arise due to modulation of the nonlinear intraseasonal oscillations by the annual cycle is demonstrated using a simple nonlinear dynamical model. The phase and the amplitude of the internal mode is unpredictable and hence may be responsible for limiting the long range predictability of the monsoon

Geometric Design and Stability of Power Networks

From the perspective of the network theory, the present work illustrates how the parametric intrinsic geometric description exhibits an exact set of pair correction functions and global correlation volume with and without the inclusion of the imaginary power flow. The Gaussian fluctuations about the equilibrium basis accomplish a well-defined, non-degenerate, curved regular intrinsic Riemannian surfaces for the purely real and the purely imaginary power flows and their linear combinations. An explicit computation demonstrates that the underlying real and imaginary power correlations involve ordinary summations of the power factors, with and without their joint effects. Novel aspect of the intrinsic geometry constitutes a stable design for the power systems.Comment: 23 pages, 11 figures, Keywords: Correlation; Geometry; Power Flow; Network; Stabilit

On possible impact of the Indian summer monsoon on the ENSO

The Indian summer monsoon (ISM) could influence the El Nino and Southern Oscillation (ENSO) only if it could induce significant surface wind anomalies in the active regions of central and eastern equatorial Pacific. Using 50-year NCEP reanalysis, it is shown that observed surface winds in the central and eastern Pacific associated 'purely' with ISM and unrelated to ENSO are very weak (~0.5m.s-1). Strong surface winds in the central and eastern Pacific following a 'strong' or 'weak' ISM, noted in some earlier composite analyses, are related not to ISM but to the concurrent sea surface temperature (SST) forcing associated with the ENSO. A long run of an atmospheric general circulation model (AGCM) without inter-annual SST forcing also show that a 'pure' ISM induces only very weak surface winds in the equatorial central and eastern Pacific. Thus, we conclude that the ISM by itself is unlikely to influence the ENSO in a significant way

Regime shift in Indian summer monsoon climatological intraseasonal oscillations

Using a high resolution daily rainfall data over Indian continent between 1951 and 2004, summer monsoon climatological intraseasonal oscillations (CISO) and its regime shift around mid seventies is investigated. Explaining 20% -40% of intraseasonal oscillation (ISO) amplitude, the summer monsoon CISO represents a significant predictable component of the monsoon ISOs. Indian monsoon CISO is characterized by a dominant northward propagating episode in both pre-seventies (1951-75, pre75) and in the post-seventies (1979-04, post79). The dominant episode starts in the beginning of July during pre75 in contrast to beginning of June during post79 period. We find that the IAV of the initial phase of both the first and the second ISO episodes worked in tandem with the changes in the northward propagation speed in producing the phase locking for the second episode during pre75 while for the first episode during post79. Change in northward propagation speed is shown to be consistent with changes in easterly vertical shear and meridional gradient of low level humidity during the two climate regimes

Mechanisms of some tropical intraseasonal oscillations

A underlying mechanism for two westward propagating tropical intraseasonal oscillations is discovered. Destabilization of equatorial normal modes by moist feedbacks, in particular, by evaporation-wind feedback, is responsible for both of them. The westward propagating 4-5 day oscillation and the quasi-biweekly oscillation result from destabilization of the mixed Rossby gravity (MRG) wave by the evaporation-wind feedback. The frequency and scale-selection of the the unstable MRG wave depend critically on the background mean wind. In mean easterlies (as in the Pacific and the Atlantic), it results in the 4-5 day oscillation while in mean westerlies (as in the Indian Ocean during northern summer) it results in the quasi-biweekly mode