55,400 research outputs found
Z_{12-I} Orbifold Compactification toward SUSY Standard Model
We explain the orbifold compactification in string models and present a
Z_{12-I} orbifold compactification toward supersymmetric standard models. We
also point out an effective R-parity from this string construction. The VEVs of
gauge singlets are chosen such that phenomenological constraints are satisfied.Comment: 13 pages with 5 figure. Talk presented at "CTP Symposium on SUSY at
LHC", Cairo, 11-14 March 200
Supersymmetric three family chiral SU(6) grand unification model from F-theory
We obtain a supersymmetric three family chiral SU(6) grand unification model
with the global family symmetry SU(3)[family] from F-theory. This model has
nice features such as all the fermion masses are reasonably generated and there
results only one pair of Higgs doublets, realizing the doublet-triplet
splitting from the family symmetry SU(3)[family]. The proton hexality is
realized toward the proton stability problem. There is a room to fit the three
gauge couplings using the F-theory flux idea and we obtain the proton lifetime
in the 10^{36-37} yr region.Comment: 5 pages, to be published in Phys. Rev.
Cosmological constant is probably adjustable in brane worlds
In the brane world scenario, possessing the self-tuning property of the
cosmological constant, we study the probability amplitude for an initial state
of the Universe to transform to final states with some curvatures. In the Kim,
Kyae and Lee model, there exists a finite range of parameters such that the
transition amplitude to a near flat universe is exponentially dominated by the
smallness of curvature, > e^{positive number}/{Lambda-bar}^2}, i.e. is
dominated by an almost flat universe of |Lambda-bar|<epsilon.Comment: 6 pages with 2 figure
Charmonium levels near threshold and the narrow state X(3872) \to \pi^{+}\pi^{-}\jpsi
We explore the influence of open-charm channels on charmonium properties, and
profile the 1:3D2, 1:3D3 and 2:1P1 charmonium candidates for X(3872). The
favored candidates, the 1:3D2 and 1:3D3 levels, both have prominent radiative
decays. The 1:3D2 might be visible in the channel, while
the dominant decay of the 1:3D3 state should be into . We propose
that additional discrete charmonium levels can be discovered as narrow
resonances of charmed and anticharmed mesons.Comment: 8 pages, 6 figures, uses RevTeX and boxedeps; few transcription
errors corrected in Tables IV and VI, three entries added in Table V, updated
references. Version to appear in Phys. Rev.
Two-Electron Linear Intersubband Light Absorption in a Biased Quantum Well
We point out a novel manifestation of many-body correlations in the linear
optical response of electrons confined in a quantum well. Namely, we
demonstrate that along with conventional absorption peak at frequency close to
intersubband energy, there exists an additional peak at double frequency. This
new peak is solely due to electron-electron interactions, and can be understood
as excitation of two electrons by a single photon. The actual peak lineshape is
comprised of a sharp feature, due to excitation of pairs of intersubband
plasmons, on top of a broader band due to absorption by two single-particle
excitations. The two-plasmon contribution allows to infer intersubband plasmon
dispersion from linear absorption experiments.Comment: 4 pages, 3 figures; published versio
Prospects for Mirage Mediation
Mirage mediation reduces the fine-tuning in the minimal supersymmetric
standard model by dynamically arranging a cancellation between anomaly-mediated
and modulus-mediated supersymmetry breaking. We explore the conditions under
which a mirage "messenger scale" is generated near the weak scale and the
little hierarchy problem is solved. We do this by explicitly including the
dynamics of the SUSY-breaking sector needed to cancel the cosmological
constant. The most plausible scenario for generating a low mirage scale does
not readily admit an extra-dimensional interpretation. We also review the
possibilities for solving the mu/Bmu problem in such theories, a potential
hidden source of fine-tuning.Comment: 14 page
Affine maps of density matrices
For quantum systems described by finite matrices, linear and affine maps of
matrices are shown to provide equivalent descriptions of evolution of density
matrices for a subsystem caused by unitary Hamiltonian evolution in a larger
system; an affine map can be replaced by a linear map, and a linear map can be
replaced by an affine map. There may be significant advantage in using an
affine map. The linear map is generally not completely positive, but the linear
part of an equivalent affine map can be chosen to be completely positive and
related in the simplest possible way to the unitary Hamiltonian evolution in
the larger system.Comment: 4 pages, title changed, sentence added, reference update
Dynamical solution to the problem at TeV scale
We introduce a new confining force (\mu-color) at TeV scale to dynamically
generate a supersymmetry preserving mass scale which would replace the \mu
parameter in the minimal supersymmetric standard model (MSSM). We discuss the
Higgs phenomenology and also the pattern of soft supersymmetry breaking
parameters allowing the correct electroweak symmetry breaking within the
\mu-color model, which have quite distinctive features from the MSSM and also
from other generalizations of the MSSM.Comment: 12 pages, REVte
Intersecting Brane World from Type I Compactification
We elaborate that general intersecting brane models on orbifolds are obtained
from type I string compactifications and their T-duals. Symmetry breaking and
restoration occur via recombination and parallel separation of branes,
preserving supersymmetry. The Ramond-Ramond tadpole cancelation and the toron
quantization constrain the spectrum as a branching of the adjoints of SO(32),
up to orbifold projections. Since the recombination changes the gauge coupling,
the single gauge coupling of type I could give rise to different coupling below
the unification scale. This is due to the nonlocal properties of the
Dirac-Born-Infeld action. The weak mixing angle sin^2 theta_W = 3/8 is
naturally explained by embedding the quantum numbers to those of SO(10).Comment: 31 pages, 5 figure
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