Lepton Flavor Violation without Supersymmetry

We study the lepton flavor violating (LFV) processes mu -> e gamma, mu -> 3e, and mu -> e conversion in nuclei in the left-right symmetric model without supersymmetry and perform the first complete computation of the LFV branching ratios B(mu -> f) to leading non-trivial order in the ratio of left- and right-handed symmetry breaking scales. To this order, B(mu -> e gamma) and B(mu -> e) are governed by the same combination of LFV violating couplings, and their ratio is naturally of order unity. We also find B(mu -> 3 e)/B(mu -> e) \sim 100 under slightly stronger assumptions. Existing limits on the branching ratios already substantially constrain mass splittings and/or mixings in the heavy neutrino sector. When combined with future collider studies and precision electroweak measurements, improved limits on LFV processes will test the viability of low-scale, non-supersymmetric LFV scenarios.Comment: 24 pages, 7 figures, 2 table

Large-scale magnetic fields, curvature fluctuations and the thermal history of the Universe

It is shown that gravitating magnetic fields affect the evolution of curvature perturbations in a way that is reminiscent of a pristine non-adiabatic pressure fluctuation. The gauge-invariant evolution of curvature perturbations is used to constrain the magnetic power spectrum. Depending on the essential features of the thermodynamic history of the Universe, the explicit derivation of the bound is modified. The theoretical uncertainty in the constraints on the magnetic energy spectrum is assessed by comparing the results obtained in the case of the conventional thermal history with the estimates stemming from less conventional (but phenomenologically allowed) post-inflationary evolutions.Comment: 21 pages, 6 included figure

Escape of black holes from the brane

TeV-scale gravity theories allow the possibility of producing small black holes at energies that soon will be explored at the LHC or at the Auger observatory. One of the expected signatures is the detection of Hawking radiation, that might eventually terminate if the black hole, once perturbed, leaves the brane. Here, we study how the `black hole plus brane' system evolves once the black hole is given an initial velocity, that mimics, for instance, the recoil due to the emission of a graviton. The results of our dynamical analysis show that the brane bends around the black hole, suggesting that the black hole eventually escapes into the extra dimensions once two portions of the brane come in contact and reconnect. This gives a dynamical mechanism for the creation of baby branes.Comment: 4 pages, 6 figure

Pentaquark implications for exotic mesons

If the exotic baryon $\Theta^+(1540)$ is a correlated $udud\bar{s}$ with $J^P = {1/2}^+$, then there should exist an exotic meson, $J^P = 1^-$ $\vartheta^+ (S=+2)$ $\to K^+K^0$ $\sim 1.6$GeV with width $O(10-100)$MeV. The $\pi_1(1400;1600)$ may be broad members of {\bf 10} $\pm$ \10bar in such a picture. Vector mesons in the 1.4 - 1.7GeV mass range are also compared with this picture

Macroscopic amplification of electroweak effects in molecular Bose-Einstein condensates

We investigate the possible use of Bose-Einstein condensates of diatomic molecules to measure nuclear spin-dependent parity violation effects, outlining a detection method based on the internal Josephson effect between molecular states of opposite parity. When applied to molecular condensates, the fine experimental control achieved in atomic bosonic Josephson junctions could provide data on anapole moments and neutral weak couplings.Comment: 5 pages. To be published Phys. Rev. A (Rapid Communication) (2012

Cosmological Hysteresis and the Cyclic Universe

A Universe filled with a homogeneous scalar field exhibits `Cosmological hysteresis'. Cosmological hysteresis is caused by the asymmetry in the equation of state during expansion and contraction. This asymmetry results in the formation of a hysteresis loop: $\oint pdV$, whose value can be non-vanishing during each oscillatory cycle. For flat potentials, a negative value of the hysteresis loop leads to the increase in amplitude of consecutive cycles and to a universe with older and larger successive cycles. Such a universe appears to possess an arrow of time even though entropy production is absent and all of the equations respect time-reversal symmetry ! Cosmological hysteresis appears to be widespread and exists for a large class of scalar field potentials and mechanisms for making the universe bounce. For steep potentials, the value of the hysteresis loop can be positive as well as negative. The expansion factor in this case displays quasi-periodic behaviour in which successive cycles can be both larger as well as smaller than previous ones. This quasi-regular pattern resembles the phenomenon of BEATS displayed by acoustic systems. Remarkably, the expression relating the increase/decrease in oscillatory cycles to the quantum of hysteresis appears to be model independent. The cyclic scenario is extended to spatially anisotropic models and it is shown that the anisotropy density decreases during successive cycles if the hysteresis loop is negative.Comment: 31 pages, 8 figures. Matches version published in Phys Rev D85, 123542 (2012

Gravitational Uncertainty and Black Hole Remnants

Possible existence of black holes remnants provides a suitable candidates for dark matter. In this paper we study the possibility of existence for such remnants. We consider quantum gravitational induced corrections of black hole's entropy and temperature to investigate the possibility of such relics. Observational scheme for detection of these remnants and their cosmological constraints are discussed.Comment: 17 pages, 6 figure

Lyman alpha absorption lines from mini pancakes

[Abridged abstract:] Recent numerical simulations show that many \lyal absorption lines of column densities \nha \la 10^{15} cm$^{-2}$ are produced in transient, mini pancakes. Such pancakes are modeled here, approximating the initial perturbation leading to the formation of the pancake as a single sinusoidal wave. The density and temperature profiles of the gas in the pancake are determined for $z_c \sim 3$, where $z_c$ is the collapse redshift. The \lyal absorption line profiles for a line of sight through the pancake are then calculated. The absorption lines in general have wings signifying bulk motions in the gas. It is shown that the deviation from a single Voigt profile is large for small H I column density lines, in which the effect of bulk motions is large. For lines with \nha > 10^{13} cm$^{-2}$, high temperature tend to wash out the signatures of bulk motion. The analytical modeling of mini pancakes associated with \lyal forest lines --- with 10^{13} \la \nha \la 10^{15} cm$^{-2}$---gives the corresponding mass scales. It is shown here that, for typical values of cosmological parameters, absorption lines with \nha \sim 10^{14} cm$^{-2}$ correspond to structures with baryonic mass of $M_b \sim 10^{10}$ M$_{\odot}$ with an overdensity of $\sim 10$ at $z \sim 3$. The value of \nha can change by a factor $\sim 3$ in the course of evolution of the pancake in time. It is also shown that there is an upper limit to \nha from a pancake due to the slow recombination rate and the importance of collisional ionization at high temperatures. Mini pancakes do not give rise to \lyal lines with \nha \ga 10^{14.5} cm$^{-2}$, for \j21=1 and $\Omega_{IGM} \sim 0.03$.Comment: Latex with aaspp4.sty (25 pages), 6 figures, Accepted for publication in The Astrophysical Journa

Physical constants and the Gurzadyan-Xue formula for the dark energy

We consider cosmological implications of the formula for the dark energy density derived by Gurzadyan and Xue which predicts a value fitting the observational one. Cosmological models with varying by time physical constants, namely, speed of light and gravitational constant and/or their combinations, are considered. In one of the models, for example, vacuum energy density induces effective negative curvature, while another one has an unusual asymptotic. This analysis also explicitely rises the issue of the meaning and content of physical units and constants in cosmological context.Comment: version corrected to match the one to appear in Modern Physics Letters

Where are the Walls?

The reported spatial variation in the fine-structure constant at high redshift, if physical, could be due to the presence of dilatonic domains, and one or more domain walls inside our horizon. An absorption spectrum of an object in a different domain from our own would be characterized by a different value of alpha. We show that while a single wall solution is statically comparable to a dipole fit, and is a big improvement over a weighted mean (despite adding 3 parameters), a two-wall solution is a far better fit (despite adding 3 parameters over the single wall solution). We derive a simple model accounting for the two-domain wall solution. The goodness of these fits is however dependent on the extra random error which was argued to account for the large scatter in most of the data. When this error is omitted, all the above solutions are poor fits to the data. When included, the solutions that exhibit a spatial dependence agree with the data much more significantly than the Standard Model; however, the Standard Model itself is not a terrible fit to the data, having a p-value of ~ 20 %