Baryon-strangeness correlations: a diagnostic of strongly interacting matter

The correlation between baryon number and strangeness elucidates the nature of strongly interacting matter, such as that formed transiently in high-energy nuclear collisions. This diagnostic can be extracted theoretically from lattice QCD calculations and experimentally from event-by-event fluctuations. The analysis of present lattice results above the critical temperature severely limits the presence of q-qbar bound states, thus supporting a picture of independent (quasi)quarks.Comment: 4 pages, 2 eps figures, Revised: several sign typos have been fixed (the PRL version is correct

Jet modification in three dimensional fluid dynamics at next-to-leading twist

The modification of the single inclusive spectrum of high transverse momentum ($p_T$) pions emanating from an ultra-relativistic heavy-ion collision is investigated. The deconfined sector is modelled using a full three dimensional (3-D) ideal fluid dynamics simulation. Energy loss of high $p_T$ partons and the ensuing modification of their fragmentation is calculated within perturbative QCD at next-to-leading twist, where the magnitude of the higher twist contribution is modulated by the entropy density extracted from the 3-D fluid dynamics simulation. The nuclear modification factor ($R_{AA}$) for pions with a $p_T \geq 8$ GeV as a function of centrality as well as with respect to the reaction plane is calculated. The magnitude of contributions to the differential $R_{AA}$ within small angular ranges, from various depths in the dense matter is extracted from the calculation and demonstrate the correlation of the length integrated density and the $R_{AA}$ from a given depth. The significance of the mixed and hadronic phase to the overall magnitude of energy loss are explored.Comment: 5 pages, 4 figures, Revte

Baryon number and strangeness: signals of a deconfined antecedent

The correlation between baryon number and strangeness is used to discern the nature of the deconfined matter produced at vanishing chemical potential in high-energy nuclear collisions at the BNL RHIC. Comparisons of results of various phenomenological models with correlations extracted from lattice QCD calculations suggest that a quasi-particle picture applies. At finite baryon densities, such as those encountered at the CERN SPS, it is demonstrated that the presence of a first-order phase transition and the accompanying development of spinodal decomposition would significantly enhance the number of strangeness carriers and the associated fluctuations.Comment: 10 pages, 4 figures, latex, to appear in the proceedings of the Workshop on Correlations and Fluctuations in Relativistic Nuclear collisions, (MIT, April 21-23,2005

Resolving the plasma profile via differential single inclusive suppression

The ability of experimental signatures to resolve the spatio-temporal profile of an expanding quark gluon plasma is studied. In particular, the single inclusive suppression of high momentum hadrons versus the centrality of a heavy-ion collision and with respect to the reaction plane in non-central collisions is critically examined. Calculations are performed in the higher twist formalism for the modification of the fragmentation functions. Radically different nuclear geometries are used. The influence of different initial gluon distributions as well as different temporal evolution scenarios on the single inclusive suppression of high momentum pions are outlined. It is demonstrated that the modification versus the reaction plane is quite sensitive to the initial spatial density. Such sensitivity remains even in the presence of a strong elliptic flow.Comment: 5 pages, 4 figures, RevTex

Unequivocal demonstration of fructose-1,6-bisphosphatase in mammalian brain

Fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase; EC 3.1.3.11) has been found in rat brain and identified unequivocally. The enzyme has been purified to 95% homogeneity by standard procedures, including adsorption to a phosphocellulose column followed by elution with substrate. The purified enzyme exhibits a broad optimum above pH 7.6. Both fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate are substrates of this enzyme; the hydrolysis of the latter occurs at about 20% of the rate of the former, and the Km for fructose 1,6-bisphosphate is approximately 1.32 × 10(-4) M. 5'-AMP, an inhibitor of other mammalian-fructose-1,6-bisphosphatases, is without effect, and in further contrast with the other enzymes there is no metal requirement for activity. Purified brain enzyme fails to crossreact with the antibody prepared against the purified liver fructose-1,6-bisphosphatase. On the other hand, antiserum produced against the brain fructose-1,6-bisphosphatase quantitatively precipitates the enzyme activity and forms precipitin bands with preparations of brain fructose-1,6-bisphosphatase

Baryonic Strangeness and Related Susceptibilities in QCD

The ratios of off-diagonal to diagonal conserved charge susceptibilities e.g., chi_{BS}/chi_{S}, chi_{QS}/chi_{S}, related to the quark flavor susceptibilities, have proven to be discerning probes of the flavor carrying degrees of freedom in hot strongly interacting matter. Various constraining relations between the different susceptibilities are derived based on the Gell-Mann-Nishijima formula and the assumption of isospin symmetry. Using generic models of deconfined matter and results form lattice QCD, it is demonstrated that the flavor carrying degrees of freedom at a temperature above 1.5T_c are quark-like quasiparticles. A new observable related by isospin symmetry to C_{BS} = -3chi_{BS}/chi_{S} and equal to it in the baryon free regime is identified. This new observable, which is blind to neutral and non-strange particles, carries the potential of being measured in relativistic heavy-ion collisions.Comment: 12 pages, 5 figures, RevTex

A comparative study of Jet-quenching Schemes

The four major approximation schemes devised to study the modification of jets in dense matter are outlined. The comparisons are restricted to basic assumptions and approximations made in each case and the calculation methodology used. Emergent underlying similarities between apparently disparate methods brought about by the approximation schemes are exposed. Parameterizations of the medium in each scheme are discussed in terms of the transport coefficient $\hat{q}$. Discrepancies between the estimates obtained from the four schemes are discussed. Recent developments in the basic theory and phenomenology of energy loss are highlighted.Comment: 12 pages, 10 figures, latex, plenary presentation at the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (QM2006), Shanghai, China Nov. 14-20, 200

Brane Gas Inflation

We consider the brane gas picture of the early universe. At later stages, when there are no winding modes and the background is free to expand, we show that a moving 3-brane, which we identify with our universe, can inflate even though it is radiation-dominated. The crucial ingredients for successful inflation are the coupling to the dilaton and the equation of state of the bulk. If we suppose the brane initially forms in a collision of higher-dimensional branes, then the spectrum of primordial density fluctuations naturally has a thermal origin.Comment: 4 pages, 1 figur

The chemical equilibration volume: measuring the degree of thermalization

We address the issue of the degree of equilibrium achieved in a high energy heavy-ion collision. Specifically, we explore the consequences of incomplete strangeness chemical equilibrium. This is achieved over a volume V of the order of the strangeness correlation length and is assumed to be smaller than the freeze-out volume. Probability distributions of strange hadrons emanating from the system are computed for varying sizes of V and simple experimental observables based on these are proposed. Measurements of such observables may be used to estimate V and as a result the degree of strangeness chemical equilibration achieved. This sets a lower bound on the degree of kinetic equilibrium. We also point out that a determination of two-body correlations or second moments of the distributions are not sufficient for this estimation.Comment: 16 pages, 15 figures, revtex

Mobile collaborative video

The emergence of pico projectors as a part of future mobile devices presents unique opportunities for collaborative settings, especially in entertainment applications, such as video playback. By aggregating pico projectors from several users, it is possible to enhance resolution, brightness, or frame rate. In this paper we present a camera-based methodology for the alignment and synchronization of multiple projectors. The approach does not require any complicated ad hoc network setup among the mobile devices. A prototype system has been set up and used to test the proposed techniques