3,756 research outputs found
Braneworld Cosmological Perturbation Theory at Low Energy
Homogeneous cosmology in the braneworld can be studied without solving bulk
equations of motion explicitly. The reason is simply because the symmetry of
the spacetime restricts possible corrections in the 4-dimensional effective
equations of motion. It would be great if we could analyze cosmological
perturbations without solving the bulk. For this purpose, we combine the
geometrical approach and the low energy gradient expansion method to derive the
4-dimensional effective action. Given our effective action, the standard
procedure to obtain the cosmological perturbation theory can be utilized and
the temperature anisotropy of the cosmic background radiation can be computed
without solving the bulk equations of motion explicitly.Comment: 10 pages, Based on a talk presented at ACRGR4, the 4th Australasian
Conference on General Relativity and Gravitation, Monash University,
Melbourne, January 2004. To appear in the proceedings, in General Relativity
and Gravitatio
Low Energy Effective Action for Horava-Witten Cosmology
As a supersymmetric extension of the Randall-Sundrum model, we consider a
5-dimensional Horava-Witten type theory, and derive its low energy effective
action. The model we consider is a two-brane system with a bulk scalar field
satisfying the BPS condition. We solve the bulk equations of motion using a
gradient expansion method, and substitute the solution into the original action
to get the 4-dimensional effective action. The resultant effective theory can
be casted into the form of Einstein gravity coupled with two scalar fields, one
arising from the radion, the degree of freedom of the inter-brane distance, and
the other from the bulk scalar field. We also clarify the relation between our
analysis and the moduli approximation.Comment: 11 page
A study of longitudinal oscillations of propellant tanks and wave propagations in feed lines. Part 1 - Propagating pressure waves in a fluid-filled cylindrical shell
Theory and equations for propagating pressure waves in liquid filled cylindrical shell
Anisotropic Power-law Inflation
We study an inflationary scenario in supergravity model with a gauge kinetic
function. We find exact anisotropic power-law inflationary solutions when both
the potential function for an inflaton and the gauge kinetic function are
exponential type. The dynamical system analysis tells us that the anisotropic
power-law inflation is an attractor for a large parameter region.Comment: 14 pages, 1 figure. References added, minor corrections include
Anisotropic Inflation from Charged Scalar Fields
We consider models of inflation with U(1) gauge fields and charged scalar
fields including symmetry breaking potential, chaotic inflation and hybrid
inflation. We show that there exist attractor solutions where the anisotropies
produced during inflation becomes comparable to the slow-roll parameters. In
the models where the inflaton field is a charged scalar field the gauge field
becomes highly oscillatory at the end of inflation ending inflation quickly.
Furthermore, in charged hybrid inflation the onset of waterfall phase
transition at the end of inflation is affected significantly by the evolution
of the background gauge field. Rapid oscillations of the gauge field and its
coupling to inflaton can have interesting effects on preheating and
non-Gaussianities.Comment: minor changes, references added, figures are modified, conforms JCAP
published versio
Macdonald operators and homological invariants of the colored Hopf link
Using a power sum (boson) realization for the Macdonald operators, we
investigate the Gukov, Iqbal, Kozcaz and Vafa (GIKV) proposal for the
homological invariants of the colored Hopf link, which include
Khovanov-Rozansky homology as a special case. We prove the polynomiality of the
invariants obtained by GIKV's proposal for arbitrary representations. We derive
a closed formula of the invariants of the colored Hopf link for antisymmetric
representations. We argue that a little amendment of GIKV's proposal is
required to make all the coefficients of the polynomial non-negative integers.Comment: 31 pages. Published version with an additional appendi
Anisotropic Inflation with Non-Abelian Gauge Kinetic Function
We study an anisotropic inflation model with a gauge kinetic function for a
non-abelian gauge field. We find that, in contrast to abelian models, the
anisotropy can be either a prolate or an oblate type, which could lead to a
different prediction from abelian models for the statistical anisotropy in the
power spectrum of cosmological fluctuations. During a reheating phase, we find
chaotic behaviour of the non-abelian gauge field which is caused by the
nonlinear self-coupling of the gauge field. We compute a Lyapunov exponent of
the chaos which turns out to be uncorrelated with the anisotropy.Comment: 16 pages, 4 figure
Black Holes and Black String-like Solutions in Codimension-2 Braneworlds
We discuss black hole solutions with a Gauss-Bonnet term in the bulk and an
induced gravity term on a thin brane of codimension-2. We show that these black
holes can be localized on the brane, and they can be extended further into the
bulk by a warp function. These solutions have regular horizons and no other
curvature singularities appear apart from the string-like ones. The projection
of the Gauss-Bonnet term on the brane imposes a constraint relation which
dictates the form of matter on the brane and in the bulk.Comment: 9 pages, no figures, plenary talk given at the 7th Friedmann
International Seminar on Gravitation and Cosmology, 29 June-5 July 2008, Joao
Pessoa, Brazil, to appear in the proceeding
NCR+ ILC3 maintain larger STAT4 reservoir via T-BET to regulate type 1 features upon IL-23 stimulation in mice
Innate lymphoid cells (ILCs) producing IL-22 and/or IL-17, designated as ILC3, comprise a heterogeneous subset of cells involved in regulation of gut barrier homeostasis and inflammation. Exogenous environmental cues in conjunction with regulated expression of endogenous factors are key determinants of plasticity of ILC3 towards the type 1 fate. Herein, by using mouse models and transcriptomic approaches, we defined at the molecular level, initial events driving ILC3 expressing natural cytotoxicity receptors (NCR+ ILC3) to acquire type 1 features. We observed that NCR+ ILC3 exhibited high basal expression of the signal-dependent transcription factor STAT4 due to T-BET, leading to predisposed potential for the type 1 response. We found that the prototypical inducer of type 3 response, IL-23, played a predominant role over IL-12 by accessing STAT4 and preferentially inducing its phosphorylation in ILC3 expressing T-BET. The early effector program driven by IL-23 was characterized by the expression of IL-22, followed by a production of IFN-γ, which relies on STAT4, T-BET and required chromatin remodeling of the Ifng locus. Altogether, our findings shed light on a feed-forward mechanism involving STAT4 and T-BET that modulates the outcome of IL-23 signaling in ILC3. This article is protected by copyright. All rights reserved
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