Small Q balls

We develop an adequate description of non-topological solitons with a small charge, for which the thin-wall approximation is not valid. There is no classical lower limit on the charge of a stable Q-ball. We examine the parameters of these small-charge solitons and discuss the limits of applicability of the semiclassical approximation.Comment: 10 pages, latex, epsf, 2 figures include

Weak-scale hidden sector and electroweak Q-balls

By extending the scalar sector of the Standard Model (SM) by a U(1) singlet, we show that the electroweak symmetry breaking enables the formation of a stable, electrically neutral, colorless Q-ball which couples to the SM particle spectrum solely through the Higgs boson. This Q-ball has mainly weak and gravitational interactions, and behaves as a collection of weakly interacting massive particles. Therefore, it can be a candidate for the dark matter in the universe.Comment: 10 pages, typos corrected, new references adde

Ribbons Around Mexican Hats

We analyze quasi-topological solitons winding around a mexican-hat potential in two space-time dimensions. They are prototypes for a large number of physical excitations, including Skyrmions of the Higgs sector of the standard electroweak model, magnetic bubbles in thin ferromagnetic films, and strings in certain non-trivial backgrounds. We present explicit solutions, derive the conditions for classical stability, and show that contrary to the naive expectation these can be satisfied in the weak-coupling limit. In this limit we can calculate the soliton properties reliably, and estimate their lifetime semiclassically. We explain why gauge interactions destabilize these solitons, unless the scalar sector is extended.Comment: 12p. Latex , Ecole Polytechnique preprint A295.02.94 and Crete preprint 94-1

Parity violation and the nature of charges

The origin of parity violation in physics is still unknown. At the present time, it is introduced in the theory by requiring that the SU(2) subgroup entering the description of interactions involves the left components. In the present contribution, one elaborates upon a suggestion made by Landau that particles and antiparticles could be like "stereo-isomeric" molecules, which would naturally provides parity violation. Particles and antiparticles could thus be combinations of the parity doublets associated with a chiral symmetry realized in the Wigner-Weyl mode. Consequences of such a description and the possible problems it could raise are examined.Comment: 3 pages, contribution to the 3rd international workshop: "From parity violation to hadronic structure and more ..." (PAVI06), to appear in the proceedings (EPJA

On the Exponentially Large Probability of Transition through the Lavrelashvili-Rubakov-Tinyakov Wormhole

The model consisting of gravitational, scalar and axionic fields is considered. It is shown that the action of the Lavrelashvili-Rubakov-Tinyakov wormhole can be made arbitrarily negative by varying the parameters of the model. This means that semiclassically calculated probability of transition through this wormhole is not exponentially small (as usual) but exponentially large.Comment: 9 pages and 1 figure in LaTeX; there is some refinement in text; the title has been changed; the figure is added to the LaTeX fil

A new source-splitting approach to the Slepian-Wolf problem

It is shown that achieving an arbitrary rate-point in the achievable region of the M-source Slepian-Wolf [1] problem may be reduced via a practical source-splitting transformation to achieving a corner point in a 2M − 1 source Slepian-Wolf problem. Moreover, each source must be split at most once. This approach extends the ideas introduced in [2] to a practical setting: it does not require common randomness shared between splitters and the decoders, the cardinality of each source split is strictly smaller than the original, and practical iterative decoding methods can achieve rates near the theoretical bound

Analytical and numerical properties of Q-balls

Stable non-topological solitons, Q-balls, are studied using analytical and numerical methods. Three different physically interesting potentials that support Q-ball solutions are considered: two typical polynomial potentials and a logarithmic potential inspired by supersymmetry. It is shown that Q-balls in these potentials exhibit different properties in the thick-wall limit where the charge of a Q-ball is typically considerably smaller than in the thin-wall limit. Analytical criteria are derived to check whether stable Q-balls exists in the thick-wall limit for typical potentials. Q-ball charge, energy and profiles are presented for each potential studied. Evaporation rates are calculated in the perfect thin-wall limit and for realistic Q-ball profiles. It is shown that in each case the evaporation rate increases with decreasing charge.Comment: 25 page

Loop Corrections to the Neutral Higgs Boson Sector of the MSSM with Explicit CP Violation

We compute one-loop corrections to the mass matrix of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model with explicit CP violation. We use the effective potential method, allowing for arbitrary splitting between squark masses. We include terms O(g^2 h^2), where g and h stand for electroweak gauge and Yukawa couplings, respectively. Leading two-loop corrections are taken into account by means of appropriately defined running quark masses.Comment: LaTeX, 12 pages incl. 3 figures. V.2: slightly rewritten to allow for a more general phase convention. Fixed some typos and added one referenc

On some new approaches to practical Slepian-Wolf compression inspired by channel coding

This paper considers the problem, first introduced by Ahlswede and Körner in 1975, of lossless source coding with coded side information. Specifically, let X and Y be two random variables such that X is desired losslessly at the decoder while Y serves as side information. The random variables are encoded independently, and both descriptions are used by the decoder to reconstruct X. Ahlswede and Körner describe the achievable rate region in terms of an auxiliary random variable. This paper gives a partial solution for the optimal auxiliary random variable, thereby describing part of the rate region explicitly in terms of the distribution of X and Y