8,374 research outputs found

### Black Holes at Future Colliders and Beyond

One of the most dramatic consequences of low-scale (~1 TeV) quantum gravity
is copious production of mini black holes at future accelerators and in
ultra-high-energy cosmic ray interactions. Hawking radiation of these black
holes is constrained mainly to our (3+1)-dimensional world and results in rich
phenomenology. We discuss tests of Wien's law of Hawking radiation, which is a
sensitive probe of the dimensionality of extra space, as well as an exciting
possibility of finding new physics in the decays of black holes.Comment: 8 pages, 4 figures, uses moriond02.sty, included. Talk given at the
XXXVIIth Rencontres de Moriond "QCD and Hadronic interactions," Les Arcs,
March 16-23, 200

### New Types of Thermodynamics from $(1+1)$-Dimensional Black Holes

For normal thermodynamic systems superadditivity $\S$, homogeneity \H and
concavity \C of the entropy hold, whereas for $(3+1)$-dimensional black holes
the latter two properties are violated. We show that $(1+1)$-dimensional black
holes exhibit qualitatively new types of thermodynamic behaviour, discussed
here for the first time, in which \C always holds, \H is always violated
and $\S$ may or may not be violated, depending of the magnitude of the black
hole mass. Hence it is now seen that neither superadditivity nor concavity
encapsulate the meaning of the second law in all situations.Comment: WATPHYS-TH93/05, Latex, 10 pgs. 1 figure (available on request), to
appear in Class. Quant. Gra

### Ultraperipheral photoproduction of vector mesons in the nuclear Coulomb field and the size of neutral vector mesons

We point out a significance of ultraperipheral photoproduction of vector
mesons in the Coulomb field of nuclei as a means of measuring the radius of the
neutral vector meson. This new contribution to the production amplitude is very
small compared to the conventional diffractive amplitude, but because of large
impact parameters inherent to the ultraperipheral Coulomb mechanism its impact
on the diffraction slope is substantial. We predict appreciable and strongly
energy dependent increase of the diffraction slope towards very small momentum
transfer.The magnitude of the effect is proportional to the mean radius squared
of the vector meson and is within the reach of high precision photoproduction
experiments, which gives a unique experimental handle on the size of vector
mesons

### Vanishing Dimensions and Planar Events at the LHC

We propose that the effective dimensionality of the space we live in depends
on the length scale we are probing. As the length scale increases, new
dimensions open up. At short scales the space is lower dimensional; at the
intermediate scales the space is three-dimensional; and at large scales, the
space is effectively higher dimensional. This setup allows for some fundamental
problems in cosmology, gravity, and particle physics to be attacked from a new
perspective. The proposed framework, among the other things, offers a new
approach to the cosmological constant problem and results in striking collider
phenomenology and may explain elongated jets observed in cosmic-ray data.Comment: v1: 5 pages revtex, 1 eps figure; v2: includes extensive discussion
on violation of Lorentz invariance, featured in a Nature editorial [Nature
466 (2010) 426] http://www.nature.com/news/2010/100720/full/466426a.html; v3:
discussion expanded, matching journal versio

### Quasi-Homogeneous Thermodynamics and Black Holes

We propose a generalized thermodynamics in which quasi-homogeneity of the
thermodynamic potentials plays a fundamental role. This thermodynamic formalism
arises from a generalization of the approach presented in paper [1], and it is
based on the requirement that quasi-homogeneity is a non-trivial symmetry for
the Pfaffian form $\delta Q_{rev}$. It is shown that quasi-homogeneous
thermodynamics fits the thermodynamic features of at least some
self-gravitating systems. We analyze how quasi-homogeneous thermodynamics is
suggested by black hole thermodynamics. Then, some existing results involving
self-gravitating systems are also shortly discussed in the light of this
thermodynamic framework. The consequences of the lack of extensivity are also
recalled. We show that generalized Gibbs-Duhem equations arise as a consequence
of quasi-homogeneity of the thermodynamic potentials. An heuristic link between
this generalized thermodynamic formalism and the thermodynamic limit is also
discussed.Comment: 39 pages, uses RevteX. Published version (minor changes w.r.t. the
original one

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