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

Vector Field and Inflation

We have investigated if the vector field can give rise to an accelerating phase in the early universe. We consider a timelike vector field with a general quadratic kinetic term in order to preserve an isotropic background spacetime. The vector field potential is required to satisfy the three minimal conditions for successful inflation: i) $\rho>0$, ii) $\rho+3P < 0$ and iii) the slow-roll conditions. As an example, we consider the massive vector potential and small field type potential as like in scalar driven inflation.Comment: 1+7pages, 3figures, To appear in the Proceedings of the CospA 2008, Kore

Towards musical interaction : 'Schismatics' for e-violin and computer.

This paper discusses the evolution of the Max/MSP patch used in schismatics (2007, rev. 2010) for electric violin (Violectra) and computer, by composer Sam Hayden in collaboration with violinist Mieko Kanno. schismatics involves a standard performance paradigm of a fixed notated part for the e-violin with sonically unfixed live computer processing. Hayden was unsatisfied with the early version of the piece: the use of attack detection on the live e-violin playing to trigger stochastic processes led to an essentially reactive behaviour in the computer, resulting in a somewhat predictable one-toone sonic relationship between them. It demonstrated little internal relationship between the two beyond an initial e-violin ‘action’ causing a computer ‘event’. The revisions in 2010, enabled by an AHRC Practice-Led research award, aimed to achieve 1) a more interactive performance situation and 2) a subtler and more ‘musical’ relationship between live and processed sounds. This was realised through the introduction of sound analysis objects, in particular machine listening and learning techniques developed by Nick Collins. One aspect of the programming was the mapping of analysis data to synthesis parameters, enabling the computer transformations of the e-violin to be directly related to Kanno’s interpretation of the piece in performance

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 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

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

Black String Perturbations in RS1 Model

We present a general formalism for black string perturbations in Randall-Sundrum 1 model (RS1). First, we derive the master equation for the electric part of the Weyl tensor $E_{\mu\nu}$. Solving the master equation using the gradient expansion method, we give the effective Teukolsky equation on the brane at low energy. It is useful to estimate gravitational waves emitted by perturbed rotating black strings. We also argue the effect of the Gregory-Laflamme instability on the brane using our formalism.Comment: 14 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

Modified Friedmann Equation and Inflation in Warped Codimension-two Braneworld

We study the Friedmann equation for the warped codimension-two braneworld background which most closely resembles the Randall-Sundrum model. Extra matter on the (Planck) 4-brane, with equation of state p_\theta=(\alpha-1)\rho for the azimuthal pressure, is required to satisfy the junction conditions. For 1 < \alpha < 5, we show that there are two static solutions to the Einstein equations for given values of the brane stress-energies. Close to the static solutions, the relation between Hubble expansion rate H and brane tension reproduces the standard 4D result for small H, but exhibits unusual deviations when H is of order the AdS curvature scale. The two static branches for 1 <\alpha < 5 are shown to come together smoothly at a maximum value of H; however the radion is shown to be unstable in the branch with higher H. This remains true even with a mechanism for stabilization of the radion, i.e., the Goldberger-Wise (GW) mechanism, since large enough H overcomes the force of stabilization. Even in the unstabilized case, cosmological constraints on the time and spatial variation of Newton's constant are typically satisfied; only fifth force constraints require the stabilization. For \alpha > 5 the model is intrinsically stable, without the need for a GW field, and in this case we show that inflationary predictions can be modified by the nonstandard Friedmann equation; in particular it is possible to get an upper limit on the spectral index, large deviations from the consistency condition between the tensor spectrum and ratio r, and large running of the spectral index even though the slow roll parameters remain small.Comment: 29 pages, 23 figure