1721697
Hadron correlators, spectral functions and thermal dilepton rates from lattice QCD
We discuss information on thermal modifications of hadron properties which can be extracted from the structure of Euclidean correlation functions of hadronic currents as well as more direct information obtained through the reconstruction of the spectral functions based on the Maximum Entropy Method.
16483183
MESON CORRELATION FUNCTIONS AT HIGH TEMPERATURES.
We present preliminary results for the correlation- and spectral functions of different meson channels on the lattice. The main focus lies on gaining control over cut-off as well as on the finite-volume effects. Extrapolations of screening masses above the deconfining temperature are guided by the result of the free (T = {infinity}) case on the lattice and in the continuum. We study the quenched non-perturbatively improved Wilson-clover fermion as well as the hypercube fermion action which might show less cut-off effects.
17931056
A study of charmonium systems across the deconfinement transition
We present results from lattice studies of charmonium. systems near the deconfinement transition temperature. On quenched isotropic lattices with lattice spacings between 0.02 and 0.05 fm, (q) over barq systems with quark masses close to the charm mass and with different spin-parity quantum numbers are studied in the temperature range 0.9T(c) - 3T(c). Results for temporal correlators of local operators, and the spectral functions constructed from them, axe discussed. For the pseudoscalar and vector channels, the correlators axe observed to change very little across the deconfinement transition, unlike in the case of the light quarks.
14557202
Phase transitions in SO(3) lattice gauge theory
The phase diagram of SO(3) lattice gauge theory is investigated by Monte Carlo techniques on both symmetric N σ 4 and asymmetric N σ 3 × N β lattices with a view (i) to understanding the relationship between the bulk transition and the deconfinement transition, and (ii) to resolving the current ambiguity about the nature of the high temperature phase. A number of tests, including an introduction of a magnetic field and measurement of different correlation functions in the phases with positive and negative values for the adjoint Polyakov line, L α , lead to the conclusion that the two phases correspond to the same physical state. Studies on lattices of different sizes reveal only one phase transition for this theory on all of them and it appears to have a deconfining nature.
11097501
Charmonium at finite temperature
Abstract We study charmoinum correlators and spectral functions at finite temperature within the quenched approximation using isotropic lattices with lattice spacing a −1 = 4.86 GeV and 9.72 GeV. Although we observe some medium modifications of the ground state charmonium spectral function above deconfinement, we find that ground state charmonia (J/ψ and η c exist in the deconfined phase at least up to temperatures as high as 1.5T.. P -wave charmonia ( χ c ) on the other hand are dissociated already at 1.12T c .
17426308
Impact of Z2 monopoles and vortices on the deconfinement transition
Abstract Suppressing Z 2 -monopoles shifts the line of deconfinement transitions in the coupling plane of the SU (2) lattice gauge theory with a mixed Villain form of action but it still continues to behave also like the bulk transition line. Separate deconfinement and bulk phase transitions are found on the same lattice, suggesting the two to be indeed coincident at higher adjoint couplings. Universality is restored when both monopoles and vortices are suppressed.
18570338
Fractal Structure of Molecular Clouds
Compelling evidence exists to show that the structure of molecular clouds is fractal in nature. In this paper, the author reiterates this view and, in addition, asserts that not only is cloud geometry fractal, but that they also have a common characteristic - they are similar in shape to the Horsehead nebula in Orion. This shape can be described by the Julia function f(x)= z^2 + c,where both z and c are complex quantities and c = -0.745429 + 0.113008i. The dynamical processes responsible for the production of these clouds seem to be turbulence followed by Brownian motion till high densities are reached, at which point structure formation is dictated by gravity. The author presents image analysis of four varied examples, namely those of the Horsehead nebula, Eagle nebula, Rosette nebula and Paley I nebula to prove her hypothesis. The images of these nebulae are analyzed for their box dimension using fractal analysis software and comparisons are made with the given Julia set.
119521185
Colors of Luminous Bulges in Cluster MS 1054–03 and Field Galaxies at Redshifts z ~ 0.83*
Using Hubble Space Telescope images, we separate the bulgelike (dubbed "pbulge") and disklike ("pdisk") components of 71 galaxies in the rich cluster MS 1054-03 and of 21 in the field. Our key finding is that luminous pbulges are very red, with rest-frame U-B ~ 0.45, while predicted colors are bluer by 0.20 mag. Moreover, these very red colors appear to be independent of environment, pbulge luminosity, pdisk color, and pbulge fraction. These results challenge any model of hierarchical galaxy formation that predicts the colors of distant (z ~ 0.8) luminous field and cluster bulges will differ. Our findings also disagree with other claims that 30% to 50% of bright bulges and elliptical galaxies at z ~ 1 are very blue (U-B ≤ 0).