1,456 research outputs found
The flavor of product-group GUTs
The doublet-triplet splitting problem can be simply solved in product-group
GUT models, using a global symmetry that distinguishes the doublets from the
triplets. Apart from giving the required mass hierarchy, this ``triplet
symmetry'' can also forbid some of the triplet couplings to matter. We point
out that, since this symmetry is typically generation-dependent, it gives rise
to non-trivial flavor structure. Furthermore, because flavor symmetries cannot
be exact, the triplet-matter couplings are not forbidden then but only
suppressed. We construct models in which the triplet symmetry gives acceptable
proton decay rate and fermion masses. In some of the models, the prediction m_b
~ m_\tau is retained, while the similar relation for the first generation is
corrected. Finally, all this can be accomplished with triplets somewhat below
the GUT scale, supplying the right correction for the standard model gauge
couplings to unify precisely.Comment: 10 page
Transition to an oscillator for double phase-conjugate mirror
Summary form only given. Some of the novel quantified characteristics for double phase conjugate mirrors are analysed including the effects of the nonlinearity on the critical dynamics (approach to saturation) and on the spatial distribution of the grating (large scale distortion of the beams and conjugation fidelity) and sensitivity to noise (seeding). The approach used also clarifies the question of linear instability and predicts a new transition to an oscillatory regime
Anderson localization of a Tonks-Girardeau gas in potentials with controlled disorder
We theoretically demonstrate features of Anderson localization in the
Tonks-Girardeau gas confined in one-dimensional (1D) potentials with controlled
disorder. That is, we investigate the evolution of the single particle density
and correlations of a Tonks-Girardeau wave packet in such disordered
potentials. The wave packet is initially trapped, the trap is suddenly turned
off, and after some time the system evolves into a localized steady state due
to Anderson localization. The density tails of the steady state decay
exponentially, while the coherence in these tails increases. The latter
phenomenon corresponds to the same effect found in incoherent optical solitons
On the nature of Coulomb corrections to the e^+e^- pair production in ultrarelativistic heavy-ion collisions
We manifest the origin of the wrong conclusion made by several groups of
authors on the absence of Coulomb corrections to the cross section of the
e^+e^- pair production in ultrarelativistic heavy-ion collisions. The source of
the mistake is connected with an incorrect passage to the limit in the
expression for the cross section. When this error is eliminated, the Coulomb
corrections do not vanish and agree with the results obtained within the
Weizs\"acker-Williams approximation.Comment: 7 pages, LaTe
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