Cosmological Solutions of Horava-Witten Theory

We discuss simple cosmological solutions of Horava-Witten theory describing the strongly coupled heterotic string. At energies below the grand-unified scale, the effective theory is five- not four-dimensional, where the additional coordinate parameterizes a S^1/Z_2 orbifold. Furthermore, it admits no homogeneous solutions. Rather, the vacuum state, appropriate for a reduction to four-dimensional supersymmetric models, is a BPS domain wall. Relevant cosmological solutions are those associated with this BPS state. In particular, such solutions must be inhomogeneous, depending on the orbifold coordinate as well as on time. We present two examples of this new type of cosmological solution, obtained by separation of variables rather that by exchange of time and radius coordinate applied to a brane solution, as in previous work. The first example represents the analog of a rolling radii solution with the radii specifying the geometry of the domain wall. This is generalized in the second example to include a nontrivial ``Ramond-Ramond'' scalar.Comment: 21 pages, Latex 2e with amsmath, minor addition

On the Friedmann Equation in Brane-World Scenarios

The Friedmann law on the brane generically depends quadratically on the brane energy density and involves a ``dark radiation'' term due to the bulk Weyl tensor. Despite its unfamiliar form, we show how it can be derived from a standard four-dimensional Brans-Dicke theory at low energy. In particular, the dark radiation term is found to depend linearly on the brane energy densities. For any equation of state on the branes, the radion evolves such as to generate radiation-dominated cosmology. The radiation-dominated era is conventional and consistent with nucleosynthesis.Comment: 4 pages. v2,v3: discussion on BBN extended, minor correction

Moving Five-Branes in Low-Energy Heterotic M-Theory

We construct cosmological solutions of four-dimensional effective heterotic M-theory with a moving five-brane and evolving dilaton and T modulus. It is shown that the five-brane generates a transition between two asymptotic rolling-radii solutions. Moreover, the five-brane motion always drives the solutions towards strong coupling asymptotically. We present an explicit example of a negative-time branch solution which ends in a brane collision accompanied by a small-instanton transition. The five-dimensional origin of some of our solutions is also discussed.Comment: 16 pages, Latex, 3 eps figure

Radion Potential and Brane Dynamics

We examine the cosmology of the Randall-Sundrum model in a dynamic setting where scalar fields are present in the bulk as well as the branes. This generates a mechanism similar to that of Goldberger-Wise for radion stabilization and the recovery of late-cosmology features in the branes. Due to the induced radion dynamics, the inflating branes roll towards the minimum of the radion potential, thereby exiting inflation and reheating the Universe. In the slow roll part of the potential, the 'TeV' branes have maximum inflation rate and energy as their coupling to the radion and bulk modes have minimum suppresion. Hence, when rolling down the steep end of the potential towards the stable point, the radion field (which appears as the inflaton of the effective 4D theory in the branes) decays very fast, reheats the Universe .This process results decayin a decrease of brane's canonical vacuum energy $\Lambda_4$. However, at the minimum of the potential $\Lambda_4$ is small but not neccessarily zero and the fine-tuning issue remains .Density perturbation constraints introduce an upper bound when the radion stabilizies. Due to the large radion mass and strong suppression to the bulk modes, moduli problems and bulk reheating do not occur. The reheat temperature and a sufficient number of e-folding constraints for the brane-universe are also satisfied. The model therefore recovers the radiation dominated FRW universe.Comment: 16 pages, 3 figures,extraneous sentences removed, 2 footnotes added, some typos correcte

Brane-world inflation without inflaton on the brane

Inspired by the Randall-Sundrum brane-world scenario, we investigate the possibility of brane-world inflation driven not by an inflaton field on the brane, but by a bulk, dilaton-like gravitational field. As a toy model for the dilaton-like gravitational field, we consider a minimally coupled massive scalar field in the bulk 5-dimensional spacetime, and look for a perturbative solution in the anti-de Sitter (AdS) background. For an adequate range of the scalar field mass, we find a unique solution that has non-trivial dependence on the 5th dimensional coordinate and that induces slow-roll inflation on the brane.Comment: 10 pages, 2 figures, final version, to be published in Phys. Rev.

Pre-big bang in M-theory

We discuss a simple cosmological model derived from M-theory. Three assumptions lead naturally to a pre-big bang scenario: (a) 11-dimensional supergravity describes the low-energy world; (b) non-gravitational fields live on a three-dimensional brane; and (c) asymptotically past triviality.Comment: 16 pages, 8 figures, LaTeX (requires epsf

Cosmological Perturbations in Brane-World Theories: Formalism

We develop a gauge-invariant formalism to describe metric perturbations in five-dimensional brane-world theories. In particular, this formalism applies to models originating from heterotic M-theory. We introduce a generalized longitudinal gauge for scalar perturbations. As an application, we discuss some aspects of the evolution of fluctuations on the brane. Moreover, we show how the five-dimensional formalism can be matched to the known four-dimensional one in the limit where an effective four-dimensional description is appropriate.Comment: 16 pages, no figure, matches version to appear in PR

Perancangan Typeface Dengan Ornamen Dan Arsitektur Candi Jabung Peninggalan Kerajaan Majapahit Jawa Timur

Indonesia merupakan negara yang kaya akan budaya. Bahasa dan aksara khas Indonesia masih digunakan dan terus berkembang di kalangan masyarakat, khususnya di pulau Jawa. Aksara atau yang sekarang dikenal dengan nama typeface sedang diminati atau trend dikalangan masyarakat sekarang ini, sedangkan keragaman tipografi lokal Indonesia tergolong masih sedikit. Pada sudut pandang seorang desainer hal ini menjadi peluang menarik untuk menjawab permasalahan tersebut, perancangan typeface dengan unsur budaya lokal Indonesia dipilih untuk memperkaya keragaman tipografi khas Indonesia. Perancangan typeface menggunakan ornamen dan arsitektur Candi Jabung sebagai inspirasi karya desain karena Candi Jabung merupakan salah satu dari banyak peninggalan-peninggalan Kerajaan Majapahit yang paling unik. Hasil perancangan typeface dengan unsur budaya lokal tersebut diharapkan dapat membantu memperkaya keragaman tipografi lokal Indonesia yang sekaligus juga membawa citra budaya lokal Indonesia ke dunia Internasional dengan adanya pengenalan typeface secara meluas menggunakan media internet

Big bang of the brane universe

Big bang of the Friedmann-Robertson-Walker (FRW)-brane universe is studied. In contrast to the spacelike initial singularity of the usual FRW universe, the initial singularity of the FRW-brane universe is point-like from the viewpoint of causality including gravitational waves propagating in the bulk. Existence of null singularities (seam singuralities) is also shown in the flat and open FRW-brane universe models.Comment: LaTeX, 11 pages, 3 EPS figure