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.Comment: 12 pages, 3 figures, requires harvmac and picte

Z boson pair production at LHC in a stabilized Randall-Sundrum scenario

We study the Z boson pair production at LHC in the Randall-Sundrum scenario with the Goldberger-Wise stabilization mechanism. It is shown that comprehensive account of the Kaluza-Klein graviton and radion effects is crucial to probe the model: The KK graviton effects enhance the cross section of $g g \to Z Z$ on the whole so that the resonance peak of the radion becomes easy to detect, whereas the RS effects on the $q\bar{q} \to Z Z$ process are rather insignificant. The $p_T$ and invariant-mass distributions are presented to study the dependence of the RS model parameters. The production of longitudinally polarized Z bosons, to which the SM contributions are suppressed, is mainly due to KK gravitons and the radion, providing one of the most robust methods to signal the RS effects. The $1 \sigma$ sensitivity bounds on $(\Lambda_\pi, m_\phi)$ with $k/M_{\rm Pl} =0.1$ are also obtained such that the effective weak scale $\Lambda_\pi$ of order 5 TeV can be experimentally probed.Comment: 28 pages, LaTex file, 18 eps figure

RS1 Cosmology as Brane Dynamics in an AdS/Schwarzschild Bulk

We explore various facets of the cosmology of the Randall-Sundrum scenario with two branes by considering the dynamics of the branes moving in a bulk AdS/Schwarzschild geometry. This approach allows us both to understand in more detail and from a different perspective the role of the stabilization of the hierarchy in the brane cosmology, as well as to extend to the situation where the metric contains a horizon. In particular, we explicitly determine how the Goldberger-Wise stabilization mechanism perturbs the background bulk geometry to produce a realistic cosmology.Comment: 9 pages, uses ReVTeX, no figure

Production and detection of three-qubit entanglement in the Fermi sea

Building on a previous proposal for the entanglement of electron-hole pairs in the Fermi sea, we show how 3 qubits can be entangled without using electron-electron interactions. As in the 2-qubit case, this electronic scheme works even if the sources are in (local) thermal equilibrium -- in contrast to the photonic analogue. The 3 qubits are represented by 4 edge-channel excitations in the quantum Hall effect (2 hole excitations plus 2 electron excitations with identical channel index). The entangler consists of an adiabatic point contact flanked by a pair of tunneling point contacts. The irreducible 3-qubit entanglement is characterized by the tangle, which is expressed in terms of the transmission matrices of the tunneling point contacts. The maximally entangled Greenberger-Horne-Zeilinger (GHZ) state is obtained for channel-independent tunnel probabilities. We show how low-frequency noise measurements can be used to determine an upper and lower bound to the tangle. The bounds become tighter the closer the electron-hole state is to the GHZ state.Comment: 8 pages including 4 figures; [2017: fixed broken postscript figures

On Adler-Bell-Jackiw Anomaly in 3-brane Scenario

We investigate the ABJ anomaly in the framework of an effective field theory for a 3-brane scenario and show that the contribution from induced gravity on the brane depends on both the topological structure of the bulk space-time and the embedding of the brane in the bulk. This fact implies the existence of a non-trivial vacuum structure of bulk quantum gravity. Furthermore, we argue that this axial gravitational anomaly may not necessarily be cancelled by choosing the matter content on the brane since it could be considered as a possible effect from bulk quantum gravity.Comment: 17 pages, RevTex, no figures. Some further misprints are correcte

Some anisotropic universes in the presence of imperfect fluid coupling with spatial curvature

We consider Bianchi VI spacetime, which also can be reduced to Bianchi types VI0-V-III-I. We initially consider the most general form of the energy-momentum tensor which yields anisotropic stress and heat flow. We then derive an energy-momentum tensor that couples with the spatial curvature in a way so as to cancel out the terms that arise due to the spatial curvature in the evolution equations of the Einstein field equations. We obtain exact solutions for the universes indefinetly expanding with constant mean deceleration parameter. The solutions are beriefly discussed for each Bianchi type. The dynamics of the models and fluid are examined briefly, and the models that can approach to isotropy are determined. We conclude that even if the observed universe is almost isotropic, this does not necessarily imply the isotropy of the fluid (e.g., dark energy) affecting the evolution of the universe within the context of general relativity.Comment: 17 pages, no figures; to appear in International Journal of Theoretical Physics; in this version (which is more concise) an equation added, some references updated and adde

Solving analytic differential equations in polynomial time over unbounded domains

In this paper we consider the computational complexity of solving initial-value problems de ned with analytic ordinary diferential equations (ODEs) over unbounded domains of Rn and Cn, under the Computable Analysis setting. We show that the solution can be computed in polynomial time over its maximal interval of de nition, provided it satis es a very generous bound on its growth, and that the function admits an analytic extension to the complex plane

Absolute Proper Motions to B~22.5: IV. Faint, Low Velocity White Dwarfs and the White Dwarf Population Density Law

The reduced proper motion diagram (RPMD) for a complete sample of faint stars with high accuracy proper motions in the North Galactic Pole field SA57 is investigated. Eight stars with very large reduced proper motions are identified as faint white dwarf candidates. We discriminate these white dwarf candidates from the several times more numerous QSOs based on proper motion and variability. We discuss the implausibility that these stars could be any kind of survey contaminant. If {\it bona fide} white dwarfs, the eight candidates found here represent a portion of the white dwarf population hitherto uninvestigated by previous surveys by virtue of the faint magnitudes and low proper motions. The newly discovered stars suggest a disk white dwarf scaleheight larger than the values of 250-350 pc typically assumed in assessments of the local white dwarf density. Both a <V/V_{max}> and a more complex maximum likelihood analysis of the spatial distribution of our likely thin disk white dwarfs yield scaleheights of 400-600 pc while at the same time give a reasonable match to the local white dwarf volume density found in other surveys. Our results could have interesting implications for white dwarfs as potential MACHO objects. We can place some direct constraints (albeit weak ones) on the contribution of halo white dwarfs to the dark matter of the Galaxy. Moreover, the elevated scale height that we measure for the thin disk could alter the interpretation of microlensing results to the extent of making white dwarfs untenable as the dominant MACHO contributor. (Abridged)Comment: 38 pages, 5 figures, to appear in April Ap