arXiv subjects

Todd Springer

Publications and source records attributed to Todd Springer.

6 recordsLinked to original sources

arXiv2015

Conserved Charge Susceptibilities in a Chemically Frozen Hadronic Gas

In a hadronic gas with three conserved charges (electric charge, baryon number, and strangeness) we employ the hadron resonance gas model to compute both diagonal and off-diagonal susceptibilities. We model the effect of chemical freeze-out in two ways: one in which all particle numbers are conserved below the chemical freeze-out temperature and one which takes into account resonance decays. We then briefly discuss possible implications these results may have on two active areas of research, hydrodynamic fluctuations and the search for the QCD critical point.

nucl-th↗

arXiv2012

Hydrodynamic fluctuations and two-point correlations

We examine correlations of energy density induced by initial state fluctuations, which are localized in both transverse and longitudinal extent. The hotspots are evolved according to hydrodynamics in a background which includes radial flow. Two-point energy density correlations from these hotspots are computed as a function of the difference in azimuthal angle and rapidity. Such localized perturbations occur naturally in the theory of hydrodynamic fluctuations and may provide insight into some features of the two-particle correlation data from RHIC and the LHC.

nucl-th↗

arXiv2010

Bulk spectral functions in single and multi-scalar gravity duals

We examine two point correlation functions involving the trace of the energy momentum tensor in five dimensional gravity dual theories supported by one or more scalar fields. A prescription for determining bulk channel spectral functions is developed. This prescription generalizes previous work which centered on one scalar field. As an application of these techniques, we investigate the bulk spectral function and corresponding sum rule in the Chamblin-Reall background. We show that, when expressed in terms of the beta function, the sum rule for the Chamblin-Reall background can be written in a form similar to the sum rule in Yang-Mills theory.

hep-th↗

arXiv2010

A shear spectral sum rule in a non-conformal gravity dual

A sum rule which relates a stress-energy tensor correlator to thermodynamic functions is examined within the context of a simple non-conformal gravity dual. Such a sum rule was previously derived using AdS/CFT for conformal $\mathcal{N} = 4$ Supersymmetric Yang-Mills theory, but we show that it does not generalize to the non-conformal theory under consideration. We provide a generalized sum rule and numerically verify its validity. A useful byproduct of the calculation is the computation of the spectral density in a strongly coupled non-conformal theory. Qualitative features of the spectral densities and implications for lattice measurements of transport coefficients are discussed.

hep-th↗

arXiv2009

Hydrodynamics of strongly coupled non-conformal fluids from gauge/gravity duality

The subject of relativistic hydrodynamics is explored using the tools of gauge/gravity duality. A brief literature review of AdS/CFT and gauge/gravity duality is presented first. This is followed by a pedagogical introduction to the use of these methods in determining hydrodynamic dispersion relations, $w(q)$, of perturbations in a strongly coupled fluid. Shear and sound mode perturbations are examined in a special class of gravity duals: those where the matter supporting the metric is scalar in nature. Analytical solutions (to order $q^4$ and $q^3$ respectively) for the shear and sound mode dispersion relations are presented for a subset of these backgrounds. The work presented here is based on previous publications by the same author, though some previously unpublished results are also included. In particular, the subleading term in the shear mode dispersion relation is analyzed using the AdS/CFT correspondence without any reference to the black hole membrane paradigm.

hep-th↗

arXiv2007

Cosmological Black Hole Formation due to QCD and Electroweak Phase Transitions

We solve dynamical equations of motion to determine the conditions under which an over-dense region in the early universe will lead to collapse to a black hole, starting from horizon crossing of the over-dense region to the point of gravitational instability. Here we focus on the sensitivity to QCD and electroweak phase transitions. We then solve rate equations to determine the mass distribution of black holes in the present universe. A second order phase transition or rapid crossover would have significant consequences only if the index of primordial density fluctuations n > 1.25. However, a first order transition would lead to a black hole dominated universe for any realistic value of n including n=1.

astro-ph↗