149 research outputs found
What can we learn from fluctuations of particle ratios?
We explain how fluctuations of ratios can constrain and falsify the statistical model of particle production in heavy ion collisions, using K/p fluctuations as an example. We define an observable capable of determining which statistical model, if any, governs freeze-out in ultrarelativistic heavy ion collisions. We calculate this observable for K/p fluctuations, and show that it should be the same for RHIC and LHC energies, as well as independent of centrality, if the Grand-Canonical statistical model is an appropriate description and chemical equilibrium applies. We describe variations of this scaling for deviations from this scenario, such as light quark chemical non-equilibrium, strange quark over-saturation and local conservation (canonical ensemble) for strange quarks. We also introduce a similar observable capable, together with the published K*/K measurement, of ascertaining if an interacting hadron gas phase governs the system between thermal and chemical freeze-out, and of ascertaining its duration and impact on hadronic chemistry
Holography in a background-independent effective theory
We discuss the meaning of the strong equivalence principle when applied to a
quantum field theory. We show that, because of unitary inequivalence of
accelerated frames, the only way for the equivalence principle to apply exactly
is to add a boundary term representing the decoherence of degrees of freedom
leaving the observable region of the bulk. We formulate the constraints
necessary for the equivalence principle to hold at the level of the partition
function and argue that, when the non-unitary part is expressed as a functional
integral over the horizon, holography arises naturally as a consequence of the
equivalence principle.Comment: Matches published versio
Azimuthal instabilities of the Gribov-Levin-Ryskin equation
We introduce the phenomenology of elliptic flow in nuclear collisions, and
argue that its scaling across energies, rapidities and system sizes could be
suggestive of a QCD-based rather than a hydrodynamical explanation. As a
hypothesis for such an explanation, we show that the GLR equation develops
unstable modes when the parton distribution function is generalized to depend
on azimuthal angle. This generally means the structure function aquires an
azimuthal dependence. We argue that this process is a plausible alternative
explanation for the origin of elliptic flow, one that naturally respects the
scaling experimentally observed.Comment: Accepted for publication, European Physical Journal
The Hawking-Page crossover in noncommutative anti-deSitter space
We study the problem of a Schwarzschild-anti-deSitter black hole in a
noncommutative geometry framework, thought to be an effective description of
quantum-gravitational spacetime. As a first step we derive the noncommutative
geometry inspired Schwarzschild-anti-deSitter solution. After studying the
horizon structure, we find that the curvature singularity is smeared out by the
noncommutative fluctuations. On the thermodynamics side, we show that the black
hole temperature, instead of a divergent behavior at small scales, admits a
maximum value. This fact implies an extension of the Hawking-Page transition
into a van der Waals-like phase diagram, with a critical point at a critical
cosmological constant size in Plank units and a smooth crossover thereafter. We
speculate that, in the gauge-string dictionary, this corresponds to the
confinement "critical point" in number of colors at finite number of flavors, a
highly non-trivial parameter that can be determined through lattice
simulations.Comment: 24 pages, 6 figure, 1 table, version matching that published on JHE
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