Extreme ultraviolet-excited time-resolved luminescence spectroscopy using an ultrafast table-top high-harmonic generation source

We present a table-top extreme ultraviolet (XUV) beamline for measuring time- and frequency-resolved XUV excited optical luminescence (XEOL) with additional femtosecond-resolution XUV transient absorption spectroscopy functionality. XUV pulses are generated via high-harmonic generation using a near-infrared pulse in a noble gas medium, and focused to excite luminescence from a solid sample. The luminescence is collimated and guided into a streak camera, where its spectral components are temporally resolved with picosecond temporal resolution. We time-resolve XUV excited luminescence and compare the results to luminescence decays excited at longer wavelengths for three different materials : (i) sodium salicylate, an often used XUV scintillator, (ii) fluorescent labeling molecule 4-carbazole benzoic acid (CB), and (iii) a zirconium metal oxo-cluster labeled with CB, which is a photoresist candidate for extreme-ultraviolet lithography. Our results establish time-resolved XEOL as a new technique to measure transient XUV-driven phenomena in solid-state samples, and identify decay mechanisms of molecules following XUV and soft-X-ray excitation

One-loop effective action for Einstein gravity in special background gauge

The one-loop effective action for Einstein gravity in a special one-parameter background gauge is calculated up to first order in a gauge parameter. It is shown that the effective action does not depend upon the gauge parameter on shell.Comment: 17 pages, Latex, no figure

Five-Brane Configurations without a Strong Coupling Regime

Five-brane distributions with no strong coupling problems and high symmetry are studied. The simplest configuration corresponds to a spherical shell of branes with S^3 geometry and symmetry. The equations of motions with delta-function sources are carefully solved in such backgrounds. Various other brane distributions with sixteen unbroken supercharges are described. They are associated to exact world-sheet superconformal field theories with domain-walls in space-time. We study the equations of gravitational fluctuations, find normalizable modes of bulk 6-d gravitons and confirm the existence of a mass gap. We also study the moduli of the configurations and derive their (normalizable) wave-functions. We use our results to calculate in a controllable fashion using holography, the two-point function of the stress tensor of little string theory in these vacua.Comment: LateX, 32 pages, 4 figures; (v2) A reference adde

Multiagent cooperation for solving global optimization problems: an extendible framework with example cooperation strategies

This paper proposes the use of multiagent cooperation for solving global optimization problems through the introduction of a new multiagent environment, MANGO. The strength of the environment lays in itsflexible structure based on communicating software agents that attempt to solve a problem cooperatively. This structure allows the execution of a wide range of global optimization algorithms described as a set of interacting operations. At one extreme, MANGO welcomes an individual non-cooperating agent, which is basically the traditional way of solving a global optimization problem. At the other extreme, autonomous agents existing in the environment cooperate as they see fit during run time. We explain the development and communication tools provided in the environment as well as examples of agent realizations and cooperation scenarios. We also show how the multiagent structure is more effective than having a single nonlinear optimization algorithm with randomly selected initial points

Disappearing Dark Matter in Brane World Cosmology: New Limits on Noncompact Extra Dimensions

We explore cosmological implications of dark matter as massive particles trapped on a brane embedded in a Randall-Sundrum noncompact higher dimension $AdS_5$ space. It is an unavoidable consequence of this cosmology that massive particles are metastable and can disappear into the bulk dimension. Here, we show that a massive dark matter particle (e.g. the lightest supersymmetric particle) is likely to have the shortest lifetime for disappearing into the bulk. We examine cosmological constraints on this new paradigm and show that disappearing dark matter is consistent (at the 95% confidence level) with all cosmological constraints, i.e. present observations of Type Ia supernovae at the highest redshift, trends in the mass-to-light ratios of galaxy clusters with redshift, the fraction of X-ray emitting gas in rich clusters, and the spectrum of power fluctuations in the cosmic microwave background. A best $2 \sigma$ concordance region is identified corresponding to a mean lifetime for dark matter disappearance of $15 \le \Gamma^{-1} \le 80$ Gyr. The implication of these results for brane-world physics is discussed.Comment: 7 pages, 7 figures, new cosmological constraints added, accepted for publication in PR

Quantum Iterated Function Systems

Iterated functions system (IFS) is defined by specifying a set of functions in a classical phase space, which act randomly on an initial point. In an analogous way, we define a quantum iterated functions system (QIFS), where functions act randomly with prescribed probabilities in the Hilbert space. In a more general setting a QIFS consists of completely positive maps acting in the space of density operators. We present exemplary classical IFSs, the invariant measure of which exhibits fractal structure, and study properties of the corresponding QIFSs and their invariant states.Comment: 12 pages, 1 figure include

The dynamics of quark-gluon plasma and AdS/CFT

In these pedagogical lectures, we present the techniques of the AdS/CFT correspondence which can be applied to the study of real time dynamics of a strongly coupled plasma system. These methods are based on solving gravitational Einstein's equations on the string/gravity side of the AdS/CFT correspondence. We illustrate these techniques with applications to the boost-invariant expansion of a plasma system. We emphasize the common underlying AdS/CFT description both in the large proper time regime where hydrodynamic dynamics dominates, and in the small proper time regime where the dynamics is far from equilibrium. These AdS/CFT methods provide a fascinating arena interrelating General Relativity phenomenae with strongly coupled gauge theory physics.Comment: 35 pages, 3 figures. Lectures at the 5th Aegean summer school, `From gravity to thermal gauge theories: the AdS/CFT correspondence'. To appear in the proceedings in `Lecture Notes in Physics

Holographic Cosmic Quintessence on Dilatonic Brane World

Recently quintessence is proposed to explain the observation data of supernova indicating a time-varying cosmological constant and accelerating universe. Inspired by this and its mysterious origin, we look for the possibility of quintessence as the holographic dark matters dominated in the late time in the brane world scenarios. We consider both the cases of static and moving brane in a dilaton gravity background. For the static brane we use the Hamilton-Jacobi method motivated by holographic renormalization group to study the intrinsic FRW cosmology on the brane and find out the constraint on the bulk potential for the quintessence. This constraint requires a negative slowly varying bulk potential which implies an anti-de Sitter-like bulk geometry and could be possibly realized from the higher dimensional supergravities or string theory. We find the similar constraint for the moving brane cases and that the quintessence on it has the effect as a mildly time-varying Newton constant.Comment: 16pages, no figure, Latex; revised version, references added, typos corrected, abstract and comments improved; final version, will appear in PR

Brane World Cosmology with Gauss-Bonnet Interaction

We study a Randall-Sundrum model modified by a Gauss-Bonnet interaction term. We consider, in particular, a Friedmann-Robertson-Walker metric on the brane and analyse the resulting cosmological scenario. It is shown that the usual Friedmann equations are recovered on the brane. The equation of state relating the enery density and the pressure is uniquely determined by the matching conditions. A cosmological solution with negative pressure is found.Comment: 9 pages, revtex styl