594 research outputs found
Moduli backreaction and supersymmetry breaking in string-inspired inflation models
We emphasize the importance of effects from heavy fields on supergravity
models of inflation. We study, in particular, the backreaction of stabilizer
fields and geometric moduli in the presence of supersymmetry breaking. Many
effects do not decouple even if those fields are much heavier than the inflaton
field. We apply our results to successful models of Starobinsky-like inflation
and natural inflation. In most scenarios producing a plateau potential it
proves difficult to retain the flatness of the potential after backreactions
are taken into account. Some of them are incompatible with non-perturbative
moduli stabilization. In natural inflation there exist a number of models which
are not constrained by backreactions at all. In those cases the correction
terms from heavy fields have the same inflaton-dependence as the uncorrected
potential, so that inflation may be possible even for very large gravitino
masses.Comment: 29 pages, 1 figure, comments added, subsection 2.3 added, published
versio
Universal time-dependent deformations of Schrodinger geometry
We investigate universal time-dependent exact deformations of Schrodinger
geometry. We present 1) scale invariant but non-conformal deformation, 2)
non-conformal but scale invariant deformation, and 3) both scale and conformal
invariant deformation. All these solutions are universal in the sense that we
could embed them in any supergravity constructions of the Schrodinger invariant
geometry. We give a field theory interpretation of our time-dependent
solutions. In particular, we argue that any time-dependent chemical potential
can be treated exactly in our gravity dual approach.Comment: 24 pages, v2: references adde
Holographic Fermi and Non-Fermi Liquids with Transitions in Dilaton Gravity
We study the two-point function for fermionic operators in a class of
strongly coupled systems using the gauge-gravity correspondence. The gravity
description includes a gauge field and a dilaton which determines the gauge
coupling and the potential energy. Extremal black brane solutions in this
system typically have vanishing entropy. By analyzing a charged fermion in
these extremal black brane backgrounds we calculate the two-point function of
the corresponding boundary fermionic operator. We find that in some region of
parameter space it is of Fermi liquid type. Outside this region no well-defined
quasi-particles exist, with the excitations acquiring a non-vanishing width at
zero frequency. At the transition, the two-point function can exhibit non-Fermi
liquid behaviour.Comment: 52 pages, 6 figures. v3: Appendix F added showing numerical
interpolation between the near-horizon region and AdS4. Additional minor
comments also adde
Localization of N=4 Superconformal Field Theory on S^1 x S^3 and Index
We provide the geometrical meaning of the superconformal index.
With this interpretation, the superconformal index can be realized
as the partition function on a Scherk-Schwarz deformed background. We apply the
localization method in TQFT to compute the deformed partition function since
the deformed action can be written as a -exact form. The
critical points of the deformed action turn out to be the space of flat
connections which are, in fact, zero modes of the gauge field. The one-loop
evaluation over the space of flat connections reduces to the matrix integral by
which the superconformal index is expressed.Comment: 42+1 pages, 2 figures, JHEP style: v1.2.3 minor corrections, v4 major
revision, conclusions essentially unchanged, v5 published versio
Natural images from the birthplace of the human eye
Here we introduce a database of calibrated natural images publicly available
through an easy-to-use web interface. Using a Nikon D70 digital SLR camera, we
acquired about 5000 six-megapixel images of Okavango Delta of Botswana, a
tropical savanna habitat similar to where the human eye is thought to have
evolved. Some sequences of images were captured unsystematically while
following a baboon troop, while others were designed to vary a single parameter
such as aperture, object distance, time of day or position on the horizon.
Images are available in the raw RGB format and in grayscale. Images are also
available in units relevant to the physiology of human cone photoreceptors,
where pixel values represent the expected number of photoisomerizations per
second for cones sensitive to long (L), medium (M) and short (S) wavelengths.
This database is distributed under a Creative Commons Attribution-Noncommercial
Unported license to facilitate research in computer vision, psychophysics of
perception, and visual neuroscience.Comment: Submitted to PLoS ON
DWSB in heterotic flux compactifications
We address the construction of non-supersymmetric vacua in heterotic
compactifications with intrinsic torsion and background fluxes. In particular,
we implement the approach of domain-wall supersymmetry breaking (DWSB)
previously developed in the context of type II flux compactifications. This
approach is based on considering backgrounds where probe NS5-branes wrapping
internal three-cycles and showing up as four-dimensional domain-walls do not
develop a BPS bound, while all the other BPS bounds characterizing the N=1
supersymmetric compactifications are preserved at tree-level. Via a scalar
potential analysis we provide the conditions for these backgrounds to solve the
ten-dimensional equations of motion including order \alpha' corrections. We
also consider backgrounds where some of the NS5-domain-walls develop a BPS
bound, show their relation to no-scale SUSY-breaking vacua and construct
explicit examples via elliptic fibrations. Finally, we consider backgrounds
with a non-trivial gaugino condensate and discuss their relation to
supersymmetric and non-supersymmetric vacua in the present context.Comment: 56 pages, 1 figur
Testing the gaugino AMSB model at the Tevatron via slepton pair production
Gaugino AMSB models-- wherein scalar and trilinear soft SUSY breaking terms
are suppressed at the GUT scale while gaugino masses adopt the AMSB form--
yield a characteristic SUSY particle mass spectrum with light sleptons along
with a nearly degenerate wino-like lightest neutralino and quasi-stable
chargino. The left- sleptons and sneutrinos can be pair produced at
sufficiently high rates to yield observable signals at the Fermilab Tevatron.
We calculate the rate for isolated single and dilepton plus missing energy
signals, along with the presence of one or two highly ionizing chargino tracks.
We find that Tevatron experiments should be able to probe gravitino masses into
the ~55 TeV range for inoAMSB models, which corresponds to a reach in gluino
mass of over 1100 GeV.Comment: 14 pages including 6 .eps figure
Holographic c-theorems in arbitrary dimensions
We re-examine holographic versions of the c-theorem and entanglement entropy
in the context of higher curvature gravity and the AdS/CFT correspondence. We
select the gravity theories by tuning the gravitational couplings to eliminate
non-unitary operators in the boundary theory and demonstrate that all of these
theories obey a holographic c-theorem. In cases where the dual CFT is
even-dimensional, we show that the quantity that flows is the central charge
associated with the A-type trace anomaly. Here, unlike in conventional
holographic constructions with Einstein gravity, we are able to distinguish
this quantity from other central charges or the leading coefficient in the
entropy density of a thermal bath. In general, we are also able to identify
this quantity with the coefficient of a universal contribution to the
entanglement entropy in a particular construction. Our results suggest that
these coefficients appearing in entanglement entropy play the role of central
charges in odd-dimensional CFT's. We conjecture a new c-theorem on the space of
odd-dimensional field theories, which extends Cardy's proposal for even
dimensions. Beyond holography, we were able to show that for any
even-dimensional CFT, the universal coefficient appearing the entanglement
entropy which we calculate is precisely the A-type central charge.Comment: 62 pages, 4 figures, few typo's correcte
Specificity protein, Sp1-mediated increased expression of Prdx6 as a curcumin-induced antioxidant defense in lens epithelial cells against oxidative stress
Peroxiredoxin 6 (Prdx6) is a pleiotropic oxidative stress-response protein that defends cells against reactive oxygen species (ROS)-induced damage. Curcumin, a naturally occurring agent, has diversified beneficial roles including cytoprotection. Using human lens epithelial cells (hLECs) and Prdx6-deficient cells, we show the evidence that curcumin protects cells by upregulating Prdx6 transcription via invoking specificity protein 1 (Sp1) activity against proapoptotic stimuli. Curcumin enhanced Sp1 and Prdx6 mRNA and protein expression in a concentration-dependent manner, as evidenced by western and real-time PCR analyses, and thereby negatively regulated ROS-mediated apoptosis by blunting ROS expression and lipid peroxidation. Bioinformatic analysis and DNA–protein binding assays disclosed three active Sp1 sites (−19/27, −61/69 and −82/89) in Prdx6 promoter. Co-transfection experiments with Sp1 and Prdx6 promoter–chloramphenicol acetyltransferase (CAT) constructs showed that CAT activity was dramatically increased in LECs or Sp1-deficient cells (SL2). Curcumin treatment of LECs enhanced Sp1 binding to its sites, consistent with curcumin-dependent stimulation of Prdx6 promoter with Sp1 sites and cytoprotection. Notably, disruption of Sp1 sites by point mutagenesis abolished curcumin transactivation of Prdx6. Also, curcumin failed to activate Prdx6 expression in the presence of Sp1 inhibitors, demonstrating that curcumin-mediated increased expression of Prdx6 was dependent on Sp1 activity. Collectively, the study may provide a foundation for developing transcription-based inductive therapy to reinforce endogenous antioxidant defense by using dietary supplements
Ion traps with enhanced optical and physical access
Small, controllable, highly accessible quantum systems can serve as probes at
the single quantum level to study multiple physical effects, for example in
quantum optics or for electric and magnetic field sensing. The applicability of
trapped atomic ions as probes is highly dependent on the measurement situation
at hand and thus calls for specialized traps. Previous approaches for ion traps
with enhanced optical access included traps consisting of a single ring
electrode or two opposing endcap electrodes. Other possibilities are planar
trap geometries, which have been investigated for Penning traps and rf-trap
arrays. By not having the electrodes lie in a common plane the optical access
in the latter cases can be substantially increased. Here, we discuss the
fabrication and experimental characterization of a novel radio-frequency (rf)
ion trap geometry. It has a relatively simple structure and provides largely
unrestricted optical and physical access to the ion, of up to 96% of the total
4pi solid angle in one of the three traps tested. We also discuss potential
applications in quantum optics and field sensing. As a force sensor, we
estimate sensitivity to forces smaller than 1 yN Hz^(-1/2).Comment: 6 pages, 3 figures. Corrections of some typos, application section
expanded to account for reviewer comment
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