arXiv subjects

Alan Kostelecky

Publications and source records attributed to Alan Kostelecky.

155 records · Page 9Linked to original sources

arXiv1995

Radial Squeezed States and Rydberg Wave Packets

We outline an analytical framework for the treatment of radial Rydberg wave packets produced by short laser pulses in the absence of external electric and magnetic fields. Wave packets of this type are localized in the radial coordinates and have p-state angular distributions. We argue that they can be described by a particular analytical class of squeezed states, called radial squeezed states. For hydrogenic Rydberg atoms, we discuss the time evolution of the corresponding hydrogenic radial squeezed states. They are found to undergo decoherence and collapse, followed by fractional and full revivals. We also present their uncertainty product and uncertainty ratio as functions of time. Our results show that hydrogenic radial squeezed states provide a suitable analytical description of hydrogenic Rydberg atoms excited by short-pulsed laser fields.

quant-ph↗

arXiv1995

Neutrino Oscillations in the Early Universe with Nonequilibrium Neutrino Distributions

Around one second after the big bang, neutrino decoupling and $e^+$-$e^-$ annihilation distort the Fermi-Dirac spectrum of neutrino energies. Assuming neutrinos have masses and can mix, we compute the distortions using nonequilibrium thermodynamics and the Boltzmann equation. The flavor behavior of neutrinos is studied during and following the generation of the distortion.

hep-ph↗

arXiv1995

Long-Term Evolution and Revival Structure of Rydberg Wave Packets for Hydrogen and Alkali-Metal Atoms

This paper begins with an examination of the revival structure and long-term evolution of Rydberg wave packets for hydrogen. We show that after the initial cycle of collapse and fractional/full revivals, which occurs on the time scale $t_{\rm rev}$, a new sequence of revivals begins. We find that the structure of the new revivals is different from that of the fractional revivals. The new revivals are characterized by periodicities in the motion of the wave packet with periods that are fractions of the revival time scale $t_{\rm rev}$. These long-term periodicities result in the autocorrelation function at times greater than $t_{\rm rev}$ having a self-similar resemblance to its structure for times less than $t_{\rm rev}$. The new sequence of revivals culminates with the formation of a single wave packet that more closely resembles the initial wave packet than does the full revival at time $t_{\rm rev}$, i.e., a superrevival forms. Explicit examples of the superrevival structure for both circular and radial wave packets are given. We then study wave packets in alkali-metal atoms, which are typically used in experiments. The behavior of these packets is affected by the presence of quantum defects that modify the hydrogenic revival time scales and periodicities. Their behavior can be treated analytically using supersymmetry-based quantum-defect theory. We illustrate our results for alkali-metal atoms with explicit examples of the revival structure for radial wave packets in rubidium.

quant-ph↗

arXiv1995

Self-Maintained Coherent Oscillations in Dense Neutrino Gases

We present analytical solutions to the nonlinear equations describing the behavior of a gas of neutrinos with two flavors. Self-maintained coherent flavor oscillations are shown to occur when the gas density exceeds a critical value determined by the neutrino masses and the mean neutrino energy in the gas. Similar oscillations may have occurred in the early Universe.

hep-ph↗

arXiv1995

Tests of Direct and Indirect CPT Violation at a B Factory

The issue of testing CPT invariance at a $B$ factory is considered. We present asymmetries that permit a clean extraction of quantities parametrizing direct and indirect CPT violation, using information from $Υ(4S)$ decay via coherent $B_d\overline{B_d}$ pairs into various final states. Estimates are given of the bounds on CPT violation that could be obtained in present and planned machines.

hep-ph↗

arXiv1995

CPT, Strings, and Meson Factories

Spontaneous breaking of CPT is possible in string theory. We show that it can arise at a level within reach of experiments at meson factories currently being built or designed. For $ϕ$, $B$, and $τ$-charm factories, we discuss the likely experimental string signatures and provide estimates of the bounds that might be attained in these machines.

hep-ph↗

arXiv1994

Quantum Defects and the Long-Term Behavior of Radial Rydberg Wave Packets

We show that a theoretical description of radial Rydberg wave packets in alkali-metal atoms based solely on hydrogenic wave functions and energies is insufficient to explain data that could be obtained in pump-probe experiments with current technology. The modifications to long-term revival times induced by quantum defects cannot be obtained by direct scaling of the hydrogenic results. Moreover, the effects of laser detuning and quantum defects are different. An alternative approach providing analytical predictions using supersymmetry-based quantum-defect theory is presented.

hep-ph↗

arXiv1994

Nuclear Null Tests for Spacelike Neutrinos

Recently, a type of null experiment for spacelike neutrinos has been proposed. We examine in detail a class of null tests involving nuclear beta decay or capture in atoms and ions. The most promising candidate systems are identified.

hep-ph↗

arXiv1993

Tachyon Hair for Two-Dimensional Black Holes

Using a combination of analytical and numerical methods, we obtain a two-dimensional spacetime describing a black hole with tachyon hair. The physical ADM mass of the black hole is finite. The presence of tachyon hair increases the Hawking temperature.

hep-th↗

arXiv1993

Condensates and Singularities in String Theory

We derive a class of solutions to the string sigma-model equations for the closed bosonic string. The tachyon field is taken to form a constant condensate and the beta-function equations at one-loop level are solved for the evolution of the metric and the dilaton. The solutions represent critical string theories in arbitrary dimensions. The spectrum of the subclass of models with a linearly rising asymptotic dilaton is found using the Feigin-Fuks method. Certain approximate solutions arising in string field theory are used to illustrate the results explicitly. An argument based on conformal invariance leads to the conjecture that that stringy corrections to at least some singular spacetimes in general relativity result in non-singular metrics. We use the singularities of the big-bang/crunch type appearing in our models to examine this conjecture.

hep-th↗

arXiv1992

CPT, Strings, and the $K \bar K$ System

This talk contains a summary of our work on dynamical CPT invariance and spontaneous CPT violation in string theories, including the possibility that stringy CPT violation could occur at levels detectable in the next generation of experiments. In particular, we present here an estimate for values of parameters for CPT violation in the kaon system.

hep-th↗