1,807 research outputs found
A Minimal Inflation Scenario
We elaborate on a minimal inflation scenario based entirely on the general
properties of supersymmetry breaking in supergravity models. We identify the
inflaton as the scalar component of the Goldstino superfield. We write
plausible candidates for the effective action describing this chiral
superfield. In particular the theory depends (apart from parameters of O(1)) on
a single free parameter: the scale of supersymmetry breaking. This can be fixed
using the amplitude of CMB cosmological perturbations and we therefore obtain
the scale of supersymmetry breaking to be 10^{12-14} GeV. The model also
incorporates explicit R-symmetry breaking in order to satisfy the slow roll
conditions. In our model the eta-problem is solved without extra fine-tuning.
We try to obtain as much information as possible in a model independent way
using general symmetry properties of the theory's effective action, this leads
to a new proposal on how to exit the inflationary phase and reheat the
Universe.Comment: matches published version (typo corrected
Current Distribution in the Three-Dimensional Random Resistor Network at the Percolation Threshold
We study the multifractal properties of the current distribution of the
three-dimensional random resistor network at the percolation threshold. For
lattices ranging in size from to we measure the second, fourth and
sixth moments of the current distribution, finding {\it e.g.\/} that
where is the conductivity exponent and is the
correlation length exponent.Comment: 10 pages, latex, 8 figures in separate uuencoded fil
Electronic transport through domain walls in ferromagnetic nanowires: Co-existence of adiabatic and non-adiabatic spin dynamics
We study the effect of a domain wall on the electronic transport in
ferromagnetic quantum wires. Due to the transverse confinement, conduction
channels arise. In the presence of a domain wall, spin up and spin down
electrons in these channels become coupled. For very short domain walls or at
high longitudinal kinetic energy, this coupling is weak, leads to very few spin
flips, and a perturbative treatment is possible. For very long domain wall
structures, the spin follows adiabatically the local magnetization orientation,
suppressing the effect of the domain wall on the total transmission, but
reversing the spin of the electrons. In the intermediate regime, we numerically
investigate the spin-dependent transport behavior for different shapes of the
domain wall. We find that the knowledge of the precise shape of the domain wall
is not crucial for determining the qualitative behavior. For parameters
appropriate for experiments, electrons with low longitudinal energy are
transmitted adiabatically while the electrons at high longitudinal energy are
essentially unaffected by the domain wall. Taking this co-existence of
different regimes into account is important for the understanding of recent
experiments.Comment: 10 pages, 6 figure
Destruction of diagonal and off-diagonal long range order by disorder in two-dimensional hard core boson systems
We use quantum Monte Carlo simulations to study the effect of disorder, in
the form of a disordered chemical potential, on the phase diagram of the hard
core bosonic Hubbard model in two dimensions. We find numerical evidence that
in two dimensions, no matter how weak the disorder, it will always destroy the
long range density wave order (checkerboard solid) present at half filling and
strong nearest neighbor repulsion and replace it with a bose glass phase. We
study the properties of this glassy phase including the superfluid density,
energy gaps and the full Green's function. We also study the possibility of
other localized phases at weak nearest neighbor repulsion, i.e. Anderson
localization. We find that such a phase does not truly exist: The disorder must
exceed a threshold before the bosons (at weak nn repulsion) are localized. The
phase diagram for hard core bosons with disorder cannot be obtained easily from
the soft core phase diagram discussed in the literature.Comment: 7 pages, 10 eps figures include
Disordered Bosons: Condensate and Excitations
The disordered Bose Hubbard model is studied numerically within the
Bogoliubov approximation. First, the spatially varying condensate wavefunction
in the presence of disorder is found by solving a nonlinear Schrodinger
equation. Using the Bogoliubov approximation to find the excitations above this
condensate, we calculate the condensate fraction, superfluid density, and
density of states for a two-dimensional disordered system. These results are
compared with experiments done with adsorbed in porous media.Comment: RevTeX, 26 pages and 10 postscript figures appended (Figure 9 has
three separate plots, so 12 postcript files altogether
Experimental probes of emergent symmetries in the quantum Hall system
Experiments studying renormalization group flows in the quantum Hall system
provide significant evidence for the existence of an emergent holomorphic
modular symmetry . We briefly review this evidence and show that,
for the lowest temperatures, the experimental determination of the position of
the quantum critical points agrees to the parts \emph{per mille} level with the
prediction from . We present evidence that experiments giving
results that deviate substantially from the symmetry predictions are not cold
enough to be in the quantum critical domain. We show how the modular symmetry
extended by a non-holomorphic particle-hole duality leads to an extensive web
of dualities related to those in plateau-insulator transitions, and we derive a
formula relating dual pairs of magnetic field strengths across any
transition. The experimental data obtained for the transition studied so far is
in excellent agreement with the duality relations following from this emergent
symmetry, and rule out the duality rule derived from the ``law of corresponding
states". Comparing these generalized duality predictions with future
experiments on other transitions should provide stringent tests of modular
duality deep in the non-linear domain far from the quantum critical points.Comment: 12 pages, 9 figure
WISP genes are members of the connective tissue growth factor family that are up-regulated in Wnt-1-transformed cells and aberrantly expressed in human colon tumors
Wnt family members are critical to many developmental processes, and components of the Wnt signaling pathway have been linked to tumorigenesis in familial and sporadic colon carcinomas. Here we report the identification of two genes, WISP-1 and WISP-2, that are up-regulated in the mouse mammary epithelial cell line C57MG transformed by Wnt-1, but not by Wnt-4. Together with a third related gene, WISP-3, these proteins define a subfamily of the connective tissue growth factor family. Two distinct systems demonstrated WISP induction to be associated with the expression of Wnt-1. These included (i) C57MG cells infected with a Wnt-1 retroviral vector or expressing Wnt-1 under the control of a tetracyline repressible promoter, and (ii) Wnt-1 transgenic mice. The WISP-1 gene was localized to human chromosome 8q24.1-8q24.3. WISP-1 genomic DNA was amplified in colon cancer cell lines and in human colon tumors and its RNA overexpressed (2- to >30-fold) in 84% of the tumors examined compared with patient-matched normal mucosa. WISP-3 mapped to chromosome 6q22-6q23 and also was overexpressed (4- to >40-fold) in 63% of the colon tumors analyzed. In contrast, WISP-2 mapped to human chromosome 20q12-20q13 and its DNA was amplified, but RNA expression was reduced (2- to >30-fold) in 79% of the tumors. These results suggest that the WISP genes may be downstream of Wnt-1 signaling and that aberrant levels of WISP expression in colon cancer may play a role in colon tumorigenesis
A Survey of Containner Breeding Mosquito Species in Kuching Area
A visual larval inspection was done from October 2010 to January 2011 to identify the common species of container-breeding mosquitoes in Kuching, Sarawak. A total of 14 areas
in Kuching were surveyed. All the 1216 larvae collected were identified. The dominant species was Ae. albopictus (79.03%), followed by Culex sp. (20.97%). The most common breeding
sources were plastic containers. The container index was the highest for Taman Budaya, Kuching (83.33%). Larval breeding habitats were found within the temperature range of 25.1â°C to 33.0â°C and pH of 3.0 to 9.9. There is no significant difference of water temperature between Ae. albopictus (30.2â°C ± 1.0) and Culex sp. (30.2â°C ± 0.6). However, the pH of water for Culex sp. (7.6 ± 0.1) was found significantly lower than that of Ae. albopictus (7.8 ± 0.9). Mean pH of natural containers (6.7 ±1.3) was significantly lower than mean pH for artificial containers (7.8 ± 1.1). Mix breeding of Ae. albopictus and Culex sp. was found in coconut and plant saucers collected from Kampung Kudei and Waterfront, respectively. Based on its dominance and versatility, we suggest that Ae. albopictus may present as a sole vector for dengue virus in Kuching
Four-point Functions of Lowest Weight CPOs in N=4 SYM_4 in Supergravity Approximation
We show that the recently found quartic action for the scalars from the
massless graviton multiplet of type IIB supergravity compactified on
AdS_5\times S^5 background coincides with the relevant part of the action of
the gauged N=8 5d supergravity on AdS_5. We then use this action to compute the
4-point function of the lowest weight chiral primary operators
\tr(\phi^{(i}\phi^{j)}) in N=4 SYM_4 at large and at strong `t Hooft
coupling.Comment: Latex, 21p, misprints are correcte
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