A remark on alpha vacua for quantum field theories on de Sitter space

It is shown that the so-called $\alpha$-vacua which have been proposed as candidates for states of free quantum fields on de Sitter space have infinitely strong fluctuations for typical observables as averaged renormalized energy momentum tensor

Non-Relativistic Superstrings: A New Soluble Sector of AdS_5xS^5

We find a new sector of string theory in AdS_5xS^5 describing non-relativistic superstrings in that geometry. The worldsheet theory of non-relativistic strings in AdS_5xS^5 is derived and shown to reduce to a supersymmetric free field theory in AdS_2. Non-relativistic string theory provides a new calculable setting in which to study holography.Comment: 29 pages, LATEX forma

Transplanckian energy production and slow roll inflation

In this paper we investigate how the energy density due to a non-standard choice of initial vacuum affects the expansion of the universe during inflation. To do this we introduce source terms in the Friedmann equations making sure that we respect the relation between gravity and thermodynamics. We find that the energy production automatically implies a slow rolling cosmological constant. Hence we also conclude that there is no well defined value for the cosmological constant in the presence of sources. We speculate that a non-standard vacuum can provide slow roll inflation on its own.Comment: 16 pages, 2 figures, version 2: minor corrections to section 4 and references adde

On Thermalization in de Sitter Space

We discuss thermalization in de Sitter space and argue, from two different points of view, that the typical time needed for thermalization is of order $R^{3}/l_{pl}^{2}$, where $R$ is the radius of the de Sitter space in question. This time scale gives plenty of room for non-thermal deviations to survive during long periods of inflation. We also speculate in more general terms on the meaning of the time scale for finite quantum systems inside isolated boxes, and comment on the relation to the Poincar\'{e} recurrence time.Comment: 14 pages, 2 figures, latex, references added. Improved discussion in section 3 adde

Electromagnetic Corrections in Partially Quenched Chiral Perturbation Theory

We introduce photons in Partially Quenched Chiral Perturbation Theory and calculate the resulting electromagnetic loop-corrections at NLO for the charged meson masses and decay constants. We also present a numerical analysis to indicate the size of the different corrections. We show that several phenomenologically relevant quantities can be calculated consistently with photons which couple only to the valence quarks, allowing the use of gluon configurations produced without dynamical photons.Comment: 11 page

Space Noncommutativity Corrections to the Cardy-Verlinde Formula

In this letter we compute the corrections to the Cardy-Verlinde formula of Schwarzschild black holes. These corrections stem from the space noncommutativity. Because the Schwarzschild black holes are non rotating, to the first order of perturbative calculations, there is no any effect on the properties of black hole due to the noncommutativity of space.Comment: 7 pages, no figures, accepted for publication in Int. J. Mod. Phys.

Mimicking transPlanckian effects in the CMB with conventional physics

We investigate the possibility that fields coupled to the inflaton can influence the primordial spectrum of density perturbations through their coherent motion. For example, the second field in hybrid inflation might be oscillating at the beginning of inflation rather than at the minimum of its potential. Although this effect is washed out if inflation lasts long enough, we note that there can be up to 30 e-foldings of inflation prior to horizon crossing of COBE fluctuations while still giving a potentially visible distortion. Such pumping of the inflaton fluctuations by purely conventional physics can resemble transPlanckian effects which have been widely discussed. The distortions which they make to the CMB could leave a distinctive signature which differs from generic effects like tilting of the spectrum.Comment: 3 pages, 4 figures; presented at PASCOS 03, TIFR, Mumbai, Indi

On the consistency of de Sitter vacua

In this paper the consistency of the de Sitter invariant $\alpha$-vacua, which have been introduced as simple tools to study the effects of transplanckian physics, is investigated. In particular possible non renormalization problems are discussed, as well as non standard properties of Greens functions. We also discuss the non thermal properties of the $\alpha$-vacua and the necessity of $\alpha$ to change. The conclusion is that non of these problems necessarily exclude an application of the $\alpha$-vacua to inflation.Comment: 12 pages, v2: minor clarifications and corrections to reference

Black hole thermalization rate from brane anti-brane model

We develop the quasi-particle picture for Schwarzchild and far from extremal black holes. We show that the thermalization equations of the black hole is recovered from the model of branes and anti-branes. This can also be viewed as a field theory explanation of the relationship between area and entropy for these black holes. As a by product the annihilation rate of branes and anti-branes is computed.Comment: 11 pages, late

Squeezed States in the de Sitter Vacuum

We discuss the treatment of squeezed states as excitations in the Euclidean vacuum of de Sitter space. A comparison with the treatment of these states as candidate no-particle states, or alpha-vacua, shows important differences already in the free theory. At the interacting level alpha-vacua are inconsistent, but squeezed state excitations seem perfectly acceptable. Indeed, matrix elements can be renormalized in the excited states using precisely the standard local counterterms of the Euclidean vacuum. Implications for inflationary scenarios in cosmology are discussed.Comment: 15 pages, no figures. One new citation in version 3; no other change