477 research outputs found
Cosmology of Antisymmetric Tensor Field in D-brane Universe
We analyze homogeneous, anisotropic cosmology driven by a self-interacting
``massive'' antisymmetric tensor field which is present in string
theories with D-branes. Time-dependent magnetic field existing in the early
universe can lead to the Bianchi type I universe. Evolutions of such a tensor
field are solved exactly or numerically in the universe dominated by vacuum
energy, radiation, and field itself. The matter-like behavior of the
field (dubbed as ``-matter'') ensures that the anisotropy disappears at late
time and thus becomes unobservable in a reasonable cosmological scenario. Such
a feature should be contrasted to the cosmology of the conventional massless
antisymmetric tensor field.Comment: 13 page
Searching for Flavored Gauge Bosons
Standard Model may allow an extended gauge sector with anomaly-free flavored
gauge symmetries, such as , , and ,
where are flavor indices. We investigate phenomenological
implications of the new flavored gauge boson in the above three
classes of gauge symmetries. Focusing on the gauge boson mass above 5 GeV, we
use the lepton universality test in the and decays, LEP
searches, LHC searches, neutrino trident production bound, and LHC
searches to put constraints on the
plane. When is involved, the LEP bounds on
the processes give the most stringent
bounds, while the LHC bound becomes the strongest constraints in the large
region when is involved. The bound from productions, which is applicable for -involved scenarios, provides
stringent bounds in the small region. One exception is the
scenario, in which case only a small region is favored due to the
lepton universality.Comment: v3: updated LHC bounds for B-3L_i model
Gauged R-symmetry, Fermion and Higgs Mass Problem
We consider the simplest model of gauge symmetry with one extra singlet field whose vacuum expectation
value breaks the horizontal -symmetry and gives rise to Yukawa
textures. The symmetry is able to provide both acceptable fermion mass
hierarchies and a natural solution to the problem only if its mixed
anomalies are cancelled by the Green-Schwarz mechanism. When the canonical
normalization of the gauge coupling constants is
assumed, the Higgs mass parameter can arise taking into
acount the uncertainty in the ultraviolet relation with . When is taken only a suppressed
value of can be obtained.Comment: 6 pages, Latex, no figure
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