152 research outputs found
Dark Matter as Dense Color Superconductor
We discuss a novel cold dark matter candidate which is formed from the
ordinary quarks during the QCD phase transition when the axion domain wall
undergoes an unchecked collapse due to the tension in the wall. If a large
number of quarks is trapped inside the bulk of a closed axion domain wall, the
collapse stops due to the internal Fermi pressure. In this case the system in
the bulk, may reach the critical density when it undergoes a phase transition
to a color superconducting phase with the ground state being the quark
condensate, similar to BCS theory. If this happens, the new state of matter
representing the diquark condensate with a large baryon number B > 10^{20}
becomes a stable soliton-like configuration. Consequently, it may serve as a
novel cold dark matter candidate.Comment: To appear in the Proceedings "Dark Matter 2002
Exact Schwarzschild-Like Solution for Yang-Mills Theories
Drawing on the parallel between general relativity and Yang-Mills theory we
obtain an exact Schwarzschild-like solution for SU(2) gauge fields coupled to a
massless scalar field. Pushing the analogy further we speculate that this
classical solution to the Yang-Mills equations shows confinement in the same
way that particles become confined once they pass the event horizon of the
Schwarzschild solution. Two special cases of the solution are considered.Comment: 11 pages LaTe
CP Violation and Matter Effect in Long Baseline Neutrino Oscillation Experiments
We show simple methods how to separate pure CP violating effect from matter
effect in long baseline neutrino oscillation experiments with three generations
of neutrinos. We give compact formulae for neutrino oscillation probabilities
assuming one of the three neutrino masses (presumably tau-neutrino mass) to be
much larger than the other masses and the effective mass due to matter effect.
Two methods are shown: One is to observe envelopes of the curves of oscillation
probabilities as functions of neutrino energy; a merit of this method is that
only a single detector is enough to determine the presence of CP violation. The
other is to compare experiments with at least two different baseline lengths;
this has a merit that it needs only narrow energy range of oscillation data.Comment: 17 pages + 9 eps figures, LaTeX, errors are correcte
Stable Neutral Fermi Ball
Fermi Ball is a kind of nontopological soliton with fermions trapped in its
domain wall, and is suggested to arises from the spontaneous symmetry breaking
of the approximate symmetry in the early universe. We find that the
neutral thin-wall Fermi Ball is stable in the limited region of the scalar
self-coupling constant and the Yukawa coupling constant . We find
that the Fermi Ball is stabilized due to the curvature effect of the domain
wall caused by the fermion sector. We also discuss whether such stable Fermi
Balls may contribute to the cold dark matter.Comment: 18 pages in RevTeX, 5 figure
The O(N) Model at Finite Temperature: Renormalization of the Gap Equations in Hartree and Large-N Approximation
The temperature dependence of the sigma meson and pion masses is studied in
the framework of the O(N) model. The Cornwall-Jackiw-Tomboulis formalism is
applied to derive gap equations for the masses in the Hartree and large-N
approximations. Renormalization of the gap equations is carried out within the
cut-off and counter-term renormalization schemes. A consistent renormalization
of the gap equations within the cut-off scheme is found to be possible only in
the large-N approximation and for a finite value of the cut-off. On the other
hand, the counter-term scheme allows for a consistent renormalization of both
the large-N and Hartree approximations. In these approximations, the meson
masses at a given nonzero temperature depend in general on the choice of the
cut-off or renormalization scale. As an application, we also discuss the
in-medium on-shell decay widths for sigma mesons and pions at rest.Comment: 21 pages, 6 figures, typos corrected and refs. added, accepted in
Journal of Physics
Parameter Degeneracies in Neutrino Oscillation Measurement of Leptonic CP and T Violation
The measurement of the mixing angle \theta_{13}, sign of \Delta m^2_{13} and
the CP or T violating phase \delta is fraught with ambiguities in neutrino
oscillation. In this paper we give an analytic treatment of the paramater
degeneracies associated with measuring the \nu_\mu -> \nu_e probability and its
CP and/or T conjugates. For CP violation, we give explicit solutions to allow
us to obtain the regions where there exist two-fold and four-fold degeneracies.
We calculate the fractional differences, \Delta \theta / \bar{\theta}, between
the allowed solutions which may be used to compare with the expected
sensitivities of the experiments. For T violation we show that there is always
a complete degeneracy between solutions with positive and negative \Delta
m^2_{13} which arises due to a symmetry and cannot be removed by observing one
neutrino oscillation probability and its T conjugate. Thus, there is always a
four fold parameter degeneracy apart from exceptional points. Explicit
solutions are also given and the fractional differences are computed. The
bi-probability CP/T trajectory diagrams are extensively used to illuminate the
nature of the degeneracies.Comment: 35 pages, Latex, 11 postscript figures, minor correction
Gauged Dimension Bubbles
Some of the peculiar electrodynamical effects associated with gauged
``dimension bubbles'' are presented. Such bubbles, which effectively enclose a
region of 5d spacetime, can arise from a 5d theory with a compact extra
dimension. Bubbles with thin domain walls can be stabilized against total
collapse by the entrapment of light charged scalar bosons inside the bubble,
extending the idea of a neutral dimension bubble to accommodate the case of a
gauged U(1) symmetry. Using a dielectric approach to the 4d dilaton-Maxwell
theory, it is seen that the bubble wall is almost totally opaque to photons,
leading to a new stabilization mechanism due to trapped photons. Photon
dominated bubbles very slowly shrink, resulting in a temperature increase
inside the bubble. At some critical temperature, however, these bubbles
explode, with a release of radiation.Comment: 14 pages, no figures; to appear in Phys.Rev.
Q-ball formation: Obstacle to Affleck-Dine baryogenesis in the gauge-mediated SUSY breaking ?
We consider the Affleck-Dine baryogenesis comprehensively in the minimal
supersymmetric standard model with gauge-mediated supersymmetry breaking.
Considering the high temperature effects, we see that the Affleck-Dine field is
naturally deformed into the form of the Q ball. In the natural scenario where
the initial amplitude of the field and the A-terms are both determined by the
nonrenormalizable superpotential, we obtain only very a narrow allowed region
in the parameter space in order to explain the baryon number of the universe
for the case that the Q-ball formation occurs just after baryon number
production. Moreover, most of the parameter sets suited have already been
excluded by current experiments. We also find new situations in which the
Q-ball formation takes place rather late compared with baryon number creation.
This situation is more preferable, since it allows a wider parameter region for
naturally consistent scenarios, although it is still difficult to realize in
the actual cosmological scenario.Comment: 27 pages, RevTeX, 21 postscript figures included. The version to be
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