arXiv subjects

Bob Holdom

Publications and source records attributed to Bob Holdom.

39 records · Page 3Linked to original sources

arXiv2001

Matter in a Warped and Oscillating Background

We examine the role of matter in an oscillating background with a warped, compact extra dimension. This background is compatible with an S^1/Z_2 orbifold structure which allows chiral fermions to be included in the scenario. When the background oscillates rapidly, the leading coupling of these oscillations is to gauge fields rather than fermions. If the decay of these oscillations were to occur today, it could provide an alternative mechanism for generating the ultra high energy cosmic rays.

hep-ph↗

arXiv2001

The Randall-Sundrum Scenario with an Extra Warped Dimension

We investigate a scenario with two four-branes embedded in six dimensions. When the metric is periodic and compact in one of the dimensions parallel to the branes, the value of the effective cosmological constant for the remaining five dimensions can assume a variety of values, determined by the dependence of the metric on the sixth dimension. The picture that emerges resembles the Randall-Sundrum model but with an extra warped dimension that allows the usual brane-bulk fine tuning to be satisfied without finely tuning any of the parameters in the underlying six dimensional theory. Although the action contains terms with four derivatives of the metric, we show that when the branes have a finite, natural thickness, such terms have only a small effect on the Randall-Sundrum structure. The presence of these four derivative terms also allows a configuration that resembles that produced by a domain wall but which results from gravity alone.

hep-ph↗

arXiv2000

The Cosmological Constant and Warped Extra Dimensions

We study the behavior of a general gravitational action, including quadratic terms in the curvature, supplemented by a compact scalar field in 4+1 dimensions. The generalized Einstein equation for this system admits solutions which are compact in one direction and Poincare invariant in the remaining directions. These solutions do not require any fine-tuning of the parameters in the action---including the cosmological constant---only that they should satisfy some mild inequalities. Some of these inequalities can be expressed in a universal form that does not depend on the number of extra compact dimensions when the scenario is generalized beyond 4+1 dimensions.

hep-th↗