2,941 research outputs found
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
Ammonia formation caused by the presence of water in the wet grinding of silicon nitride powder
Si3 N4 powder (amorphous, alpha-, and beta-Si3 N4) was mixed with MeOH containing 8.87 mol. % H2O and ground. The NH3 generation rapidly increased after a grinding time of 100 hours. Silicon nitride sintered material was chosen as one of the high temperature, high strength structural materials and studies of the control of the raw material powder, preparation of the sintered body (finding the right assistant, hot press, high pressure sintering, fracture toughness and oxidation at high temperature were performed
The MacMahon R-matrix
We introduce an -matrix acting on the tensor product of MacMahon
representations of Ding-Iohara-Miki (DIM) algebra
. This -matrix acts on pairs
of Young diagrams and retains the nice symmetry of the DIM algebra under
the permutation of three deformation parameters , and
. We construct the intertwining operator for a tensor product of
the horizontal Fock representation and the vertical MacMahon representation and
show that the intertwiners are permuted using the MacMahon -matrix.Comment: 39 page
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
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 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
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