Microscopic Black Hole Production in TeV-Scale Gravity

Models with extra spatial dimensions and TeV-scale gravity offer the first opportunity to test the conjecture of black hole formation in trans-Planckian energy scattering with small impact parameters. After a brief review of gravitational scattering at ultrahigh energies and scenarios of TeV-scale gravity, search strategies at the LHC, at the Pierre Auger (cosmic ray) Observatory and at the neutrino telescopes AMANDA/IceCube are illustrated with the simplest but nevertheless representative example: production of Schwarzschild black holes and their observation via Hawking radiation in the large extra dimension scenario. Some more general features of the production of higher-dimensional black holes and/or uncertainties in the estimates are also outlined.Comment: 18 pages, 5 figures; Talk presented at XXX ITEP Winter School of Physics, Moscow, Russia, February 2002, references adde

"Exotic" quantum effects in the laboratory?

This Article provides a brief (non-exhaustive) review of some recent developments regarding the theoretical and possibly experimental study of "exotic" quantum effects in the laboratory with special emphasis on cosmological particle creation, Hawking radiation, and the Unruh effect.Comment: 5 page

The Cosmological Mean Density and its Local Variations Probed by Peculiar Velocities

Peculiar velocities thoughout the region of the local supercluster are reconstructed by two different orbit-retracing methods. The requirement of the optimal correlation between the radial components of reconstructed velocities and the observed peculiar velocities derived from our extensive new catalog of distances puts stringent constraints on the values of the cosmological parameters. Our constraints intersect those from studies of microwave background fluctuations and statistical properties of galaxy clustering: the ensemble of constraints are consistent with Omega_m=0.22\pm 0.02. While motions throughout the Local Supercluster provide a measure of the mean ratio of mass to light, there can be large local fluctuations. Our reconstruction of the infall velocities in the immediate vicinity of the Virgo Cluster shows that there is a mass-to-light anomaly of a factor of 3 to 6 between groups in the general field environment and the heavily populated Virgo Cluster.Comment: 4 pages, 2 figures, version to appear in Astrophysical Journal Letter

Selfgravitating Gas Spheres in a Box and Relativistic Clusters: Relation between Dynamical and Thermodynamical Stability

We derive a variational principle for the dynamical stability of a cluster as a gas sphere in a box. Newtonian clusters are always dynamically stable and, for relativistic clusters, the relation between dynamical and thermodynamical instabilities is analyzed. The boundaries between dynamically and thermodynamically stable and unstable models are found numerically for relativistic stellar systems with different cut off parameters. A criterion based on binding energy curve is used for determination of the boundary of dynamical stability.Comment: 10 figure

Heating of the intergalactic medium due to structure formation

We estimate the heating of the intergalactic medium due to shocks arising from structure formation. Heating of the gas outside the collapsed regions, with small overdensities (${n_b \over {\bar n_b}}\ll 200$) is considered here, with the aid of Zel'dovich approximation. We estimate the equation of state of this gas, relating the density with its temperature, and its evolution in time, considering the shock heating due to one-$\sigma$ density peaks as being the most dominant. We also estimate the mass fraction of gas above a given temperature as a function of redshift. We find that the baryon fraction above $10^6$ K at $z=0$ is $\sim 10$. We estimate the integrated Sunyaev-Zel'dovich distortion from this gas at present epoch to be of order $10^{-6}$.Comment: 5 pages (3 figs), To appear in MNRAS (pink pages

Origin of Correlations between Central Black Holes Masses and Galactic Bulge Velocity Dispersions

We argue that the observed correlations between central black holes masses M_{BH} and galactic bulge velocity dispersions \sigma_e in the form M_{BH}\propto\sigma_e^4 may witness on the pregalactic origin of massive black holes. Primordial black holes would be the centers for growing protogalaxies which experienced multiple mergers with ordinary galaxies. This process is accompanied by the merging of black holes in the galactic nuclei.Comment: 6 pages, 1 figure, submitted to Astron. and Astrophys. Transaction

Coherent control of population transfer between communicating defects

Population transfer between two identical, communicating defects in a one-dimensional tight-binding lattice can be systematically controlled by external time-periodic forcing. Employing a force with slowly changing amplitude, the time it takes to transfer a particle from one defect to the other can be altered over several orders of magnitude. An analytical expression is derived which shows how the forcing effectively changes the energy splitting between the defect states, and numerical model calculations illustrate the possibility of coherent control of the transfer.Comment: 7 pages, 6 figures, to appear in Phys. Rev.

Bianchi Type III String Cosmological Models with Time Dependent Bulk Viscosity

Bianchi type III string cosmological models with bulk viscous fluid for massive string are investigated. To get the determinate model of the universe, we have assumed that the coefficient of bulk viscosity ($\xi$) is inversely proportional to the expansion ($\theta$) in the model and expansion ($\theta$) in the model is proportional to the shear ($\sigma$). This leads to $B = \ell C^{n}$, $\ell$ and $n$ are constants. The behaviour of the model in presence and absence of bulk viscosity, is discussed. The physical implications of the models are also discussed in detail.Comment: 11 pages, no figur

Continuum and Symmetry-Conserving Effects in Drip-line Nuclei Using Finite-range Forces

We report the first calculations of nuclear properties near the drip-lines using the spherical Hartree-Fock-Bogoliubov mean-field theory with a finite-range force supplemented by continuum and particle number projection effects. Calculations were carried out in a basis made of the eigenstates of a Woods-Saxon potential computed in a box, thereby garanteeing that continuum effects were properly taken into account. Projection of the self-consistent solutions on good particle number was carried out after variation, and an approximation of the variation after projection result was used. We give the position of the drip-lines and examine neutron densities in neutron-rich nuclei. We discuss the sensitivity of nuclear observables upon continuum and particle-number restoration effects.Comment: 5 pages, 3 figures, Phys. Rev. C77, 011301(R) (2008

Nuclear Halos and Drip Lines in Symmetry-Conserving Continuum HFB Theory

We review the properties of nuclear halos and nuclear skins in drip line nuclei in the framework of the spherical Hartree-Fock-Bogoliubov theory with continuum effects and projection on good particle number with the Gogny force. We first establish the position of the un-projected HFB drip lines for the two most employed parametrizations of the Gogny force and show that the use of finite-range interactions leads almost always to small-sized halos, even in the least bound nuclei, which is in agreement with most mean-field predictions. We also discuss the size of the neutron skin at the drip line and its relation to neutron asymmetry. The impact of particle-number projection and its conceptual consequences near the drip line are analyzed in detail. In particular, we discuss the role of the chemical potential in a projected theory and the criteria required to define the drip line. We show that including particle number projection can shift the latter, in particular near closed shells. We notice that, as a result, the size of the halo can be increased due to larger pairing correlations. However, combining the most realistic pairing interaction, a proper treatment of the continuum and particle number projection does not permit to reproduce the very large halos observed in very light nuclei.Comment: Re-submitted to Phys. Rev. C after Referee's review. Layout of figures changed to cope with editor's requirement