179 research outputs found
Higgs bosons near 125 GeV in the NMSSM with constraints at the GUT scale
We study the NMSSM with universal Susy breaking terms (besides the Higgs
sector) at the GUT scale. Within this constrained parameter space, it is not
difficult to find a Higgs boson with a mass of about 125 GeV and an enhanced
cross section in the diphoton channel. An additional lighter Higgs boson with
reduced couplings and a mass <123 GeV is potentially observable at the LHC. The
NMSSM-specific Yukawa couplings lambda and kappa are relatively large and
tan(beta) is small, such that lambda, kappa and the top Yukawa coupling are of
order 1 at the GUT scale. The lightest stop can be as light as 105 GeV, and the
fine-tuning is modest. WMAP constraints can be satisfied by a dominantly
higgsino-like LSP with substantial bino, wino and singlino admixtures and a
mass of ~60-90 GeV, which would potentially be detectable by XENON100.Comment: 20 pages, 14 figure
Flavor mixing in the gluino coupling and the nucleon decay
Flavor mixing in the quark-squark-gluino coupling is studied for the minimal
SU(5) SUGRA-GUT model and applied to evaluation of the nucleon lifetime. All
off-diagonal (generation mixing) elements of Yukawa coupling matrices and of
squark/slepton mass matrices are included in solving numerically one-loop
renormalization group equations for MSSM parameters, and the parameter region
consistent with the radiative electroweak symmetry breaking condition is
searched. It is shown that the flavor mixing in the gluino coupling for a large
is of the same order of magnitude as the corresponding
Kobayashi-Maskawa matrix element in both up-type and down-type sector. There
exist parameter regions where the nucleon decay amplitudes for charged lepton
modes are dominated by the gluino dressing process, while for all the examined
regions the neutrino mode amplitudes are dominated by the wino dressing over
the gluino dressing.Comment: 24 pages, LaTeX, figures are available upon request.
ICRR-Report-317-94-1
Scalar Hair of Global Defect and Black Brane World
We consider a complex scalar field in (p+3)-dimensional bulk with a negative
cosmological constant and study global vortices in two extra-dimensions. We
reexamine carefully the coupled scalar and Einstein equations, and show that
the boundary value of scalar amplitude at infinity of the extra-dimensions
should be smaller than vacuum expectation value. The brane world has a
cigar-like geometry with an exponentially decaying warp factor and a flat thick
p-brane is embedded. Since a coordinate transformation identifies the obtained
brane world as a black p-brane world bounded by a horizon, this strange
boundary condition of the scalar amplitude is understood as existence of a
short scalar hair.Comment: 26 pages, 2 figure
Defect Conformal Field Theory and Locally Localized Gravity
Gravity may be "locally localized" over a wide range of length scales on a
d-dimensional anti-de Sitter (AdS) brane living inside AdS_{d+1}. In this paper
we examine this phenomenon from the point of view of the holographic dual
"defect conformal field theory". The mode expansion of bulk fields on the
gravity side is shown to be precisely dual to the "boundary operator product
expansion" of operators as they approach the defect. From the field theory
point of view, the condition for localization is that a "reduced operator"
appearing in this expansion acquires negative anomalous dimension. In
particular, a very light localized graviton exists when a mode arising from the
reduction of the ambient stress-energy tensor to the defect has conformal
dimension Delta ~ d-1. The part of the stress tensor containing the defect
dynamics has dimension Delta = d-1 in the free theory, but we argue that it
acquires an anomalous dimension in the interacting theory, and hence does not
participate in localization in the regime of small backreaction of the brane.
We demonstrate that such an anomalous dimension is consistent with the
conservation of the full stress-energy tensor. Finally, we analyze how to
compute the anomalous dimensions of reduced operators from gravity at leading
order in the interactions with the brane.Comment: 38 pages, LaTeX, 5 figures. v2: typos fixe
A Cosmology of the Brane World
We develop a possible cosmology for a Universe with n additional spatial
dimensions of variable scale, and an associated scalar field, the radion, which
is distinct from the field responsible for inflation, the inflaton. Based on a
particular ansatz for the effective potential for the inflaton and radion
(which may emerge in string theory), we show that the early expansion of the
Universe may proceed in three stages. First, the radion becomes trapped at a
value much smaller than the size of the extra dimensions today. Second, the
Universe expands exponentially, but with a Planck mass smaller than its present
value. Because the Planck mass during inflation is small, density fluctuations
in agreement with observations can arise naturally. Third, when inflation ends,
the Universe reheats, and the radion becomes free to expand once more. During
the third phase the Universe is ``radiation-dominated'' and tends toward a
fixed-point evolutionary model in which the radion grows but the temperature
remains unchanged. Ultimately, the radion becomes trapped once again at its
present value, and a short period of exponential expansion, which we identify
with the electroweak phase transition, ensues. Once this epoch is over, the
Universe reheats to a temperature of order the electroweak scale, and the
mature Universe evolves as in standard cosmological models. We show that the
present day energy density in radions can be smaller than the closure density
if the second inflationary epoch lasts about 8 e-foldings or more; the
present-day radion mass turns out to be small (less than or of the order of an
eV, depending on parameters). We argue that although our model envisages
considerable time evolution in the Planck mass, substantial spatial
fluctuations in Newton's constant are not produced.Comment: 38 pages, 2 figures, submitted to Phys Rev D. Typos corrected,
references adde
A criterion for admissible singularities in brane world
When gravity couples to scalar fields in Anti-de Sitter space, the geometry
becomes non-AdS and develops singularities generally. We propose a criterion
that the singularity is physically admissible if the integral of the on-shell
Lagrangian density over the finite range is finite everywhere. For all classes
of the singularities studied here, the criterion suggested in this paper
coincides with an independent proposal made by Gubser that the potential should
be bounded from above in the solution. This gives a reason why Gubser's
conjecture works.Comment: 14 pages, revtex, 1 table, references added, two other criteria
include
A single sub-km Kuiper Belt object from a stellar Occultation in archival data
The Kuiper belt is a remnant of the primordial Solar System. Measurements of
its size distribution constrain its accretion and collisional history, and the
importance of material strength of Kuiper belt objects (KBOs). Small, sub-km
sized, KBOs elude direct detection, but the signature of their occultations of
background stars should be detectable. Observations at both optical and X-ray
wavelengths claim to have detected such occultations, but their implied KBO
abundances are inconsistent with each other and far exceed theoretical
expectations. Here, we report an analysis of archival data that reveals an
occultation by a body with a 500 m radius at a distance of 45 AU. The
probability of this event to occur due to random statistical fluctuations
within our data set is about 2%. Our survey yields a surface density of KBOs
with radii larger than 250 m of 2.1^{+4.8}_{-1.7} x 10^7 deg^{-2}, ruling out
inferred surface densities from previous claimed detections by more than 5
sigma. The fact that we detected only one event, firmly shows a deficit of
sub-km sized KBOs compared to a population extrapolated from objects with r>50
km. This implies that sub-km sized KBOs are undergoing collisional erosion,
just like debris disks observed around other stars.Comment: To appear in Nature on December 17, 2009. Under press embargo until
1800 hours London time on 16 December. 19 pages; 7 figure
First Results From The Taiwanese-American Occultation Survey (TAOS)
Results from the first two years of data from the Taiwanese-American
Occultation Survey (TAOS) are presented. Stars have been monitored
photometrically at 4 Hz or 5 Hz to search for occultations by small (~3 km)
Kuiper Belt Objects (KBOs). No statistically significant events were found,
allowing us to present an upper bound to the size distribution of KBOs with
diameters 0.5 km < D < 28 km.Comment: 5 pages, 5 figure, accepted in Ap
The TAOS Project: Upper Bounds on the Population of Small KBOs and Tests of Models of Formation and Evolution of the Outer Solar System
We have analyzed the first 3.75 years of data from TAOS, the Taiwanese
American Occultation Survey. TAOS monitors bright stars to search for
occultations by Kuiper Belt Objects (KBOs). This dataset comprises 5e5
star-hours of multi-telescope photometric data taken at 4 or 5 Hz. No events
consistent with KBO occultations were found in this dataset. We compute the
number of events expected for the Kuiper Belt formation and evolution models of
Pan & Sari (2005), Kenyon & Bromley (2004), Benavidez & Campo Bagatin (2009),
and Fraser (2009). A comparison with the upper limits we derive from our data
constrains the parameter space of these models. This is the first detailed
comparison of models of the KBO size distribution with data from an occultation
survey. Our results suggest that the KBO population is comprised of objects
with low internal strength and that planetary migration played a role in the
shaping of the size distribution.Comment: 18 pages, 16 figures, Aj submitte
Vanishing of cosmological constant and fully localized gravity in a Brane World with extra time(s)
We construct an intersecting brane configuration in six-dimensional space
with one extra space-like and one extra time-like dimensions. With a certain
additional symmetry imposed on the extra space-time we have found that
effective four-dimensional cosmological constant vanishes automatically,
providing the static solution with gravity fully localized at the intersection
region as there are no propagating massive modes of graviton. In this way, the
same symmetry allows us to eliminate tachyonic states of graviton from the
spectrum of the effective four-dimensional theory, thus avoiding
phenomenological difficulties comming from the matter instability usually
induced in theories with extra time-like dimensions.Comment: 15 pages, comments and references added, version accepted in Phys.
Lett.
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