A prototype for dS/CFT

We consider dS_2/CFT_1 where the asymptotic symmetry group of the de Sitter spacetime contains the Virasoro algebra. We construct representations of the Virasoro algebra realized in the Fock space of a massive scalar field in de Sitter, built as excitations of the Euclidean vacuum state. These representations are unitary, without highest weight, and have vanishing central charge. They provide a prototype for a new class of conformal field theories dual to de Sitter backgrounds in string theory. The mapping of operators in the CFT to bulk quantities is described in detail. We comment on the extension to dS_3/CFT_2.Comment: 17 pages, revtex

Extended Quintessence with non-minimally coupled phantom scalar field

We investigate evolutional paths of an extended quintessence with a non-minimally coupled phantom scalar field $\psi$ to the Ricci curvature. The dynamical system methods are used to investigate typical regimes of dynamics at the late time. We demonstrate that there are two generic types of evolutional scenarios which approach the attractor (a focus or a node type critical point) in the phase space: the quasi-oscillatory and monotonic trajectories approach to the attractor which represents the FRW model with the cosmological constant. We demonstrate that dynamical system admits invariant two-dimensional submanifold and discussion that which cosmological scenario is realized depends on behavior of the system on the phase plane $(\psi, \psi')$. We formulate simple conditions on the value of coupling constant $\xi$ for which trajectories tend to the focus in the phase plane and hence damping oscillations around the mysterious value $w=-1$. We describe this condition in terms of slow-roll parameters calculated at the critical point. We discover that the generic trajectories in the focus-attractor scenario come from the unstable node. It is also investigated the exact form of the parametrization of the equation of state parameter $w(z)$ (directly determined from dynamics) which assumes a different form for both scenarios.Comment: revtex4, 15 pages, 9 figures; (v2) published versio

The Principle of Non-Gravitating Vacuum Energy and some of its consequences

For Einstein's General Relativity (GR) or the alternatives suggested up to date the vacuum energy gravitates. We present a model where a new measure is introduced for integration of the total action in the D-dimensional space-time. This measure is built from D scalar fields $\varphi_{a}$. As a consequence of such a choice of the measure, the matter lagrangian $L_{m}$ can be changed by adding a constant while no gravitational effects, like a cosmological term, are induced. Such Non-Gravitating Vacuum Energy (NGVE) theory has an infinite dimensional symmetry group which contains volume-preserving diffeomorphisms in the internal space of scalar fields $\varphi_{a}$. Other symmetries contained in this symmetry group, suggest a deep connection of this theory with theories of extended objects. In general {\em the theory is different from GR} although for certain choices of $L_{m}$, which are related to the existence of an additional symmetry, solutions of GR are solutions of the model. This is achieved in four dimensions if $L_{m}$ is due to fundamental bosonic and fermionic strings. Other types of matter where this feature of the theory is realized, are for example: scalars without potential or subjected to nonlinear constraints, massless fermions and point particles. The point particle plays a special role, since it is a good phenomenological description of matter at large distances. de Sitter space is realized in an unconventional way, where the de Sitter metric holds, but such de Sitter space is supported by the existence of a variable scalar field which in practice destroys the maximal symmetry. The only space - time where maximal symmetry is not broken, in a dynamical sense, is Minkowski space. The theory has non trivial dynamics in 1+1 dimensions, unlike GR.Comment: 23 page

Trans-Planckian wimpzillas

Two previously proposed conjectures--gravitational trans-Planckian particle creation in the expanding universe, and the existence of ultra-heavy stable particles with masses up to the Planck scale (wimpzillas)--are combined in a proposal for trans-Planckian particle creation of wimpzillas. This new scenario leads to a huge enhancement in their production compared to mechanisms put forward earlier. As a result, it requires the trans-Planckian particle creation parameter to be rather small to avoid overproduction of such particles, much less than that is required for observable effects in the primordial perturbation spectrum. This ensures also that wimpzillas are mainly created at the end of primordial inflation. Conditions under which trans-Planckian wimpzillas can constitute the present dark matter are determined.Comment: Replaced with the version to be published in JCAP. Division into sections introduced, discussion expanded, references added, conclusions unchange

Passive sorting of asteroid material using solar radiation pressure

Understanding dust dynamics in asteroid environments is key for future science missions to asteroids and, in the long-term, also for asteroid exploitation. This paper proposes a novel way of manipulating asteroid material by means of solar radiation pressure (SRP). We envisage a method for passively sorting material as a function of its grain size where SRP is used as a passive in-situ ‘mass spec-trometer’. The analysis shows that this novel method allows an effective sorting of regolith material. This has immediate applications for sample return, and in-situ resource utilisation to separate different regolith particle sizes

Induced vacuum energy-momentum tensor in the background of a d-2 - brane in d+1 - dimensional space-time

Charged scalar field is quantized in the background of a static d-2 - brane which is a core of the magnetic flux lines in flat d+1 - dimensional space-time. We find that vector potential of the magnetic core induces the energy-momentum tensor in the vacuum. The tensor components are periodic functions of the brane flux and holomorphic functions of space dimension. The dependence on the distance from the brane and on the coupling to the space-time curvature scalar is comprehensively analysed.Comment: 32 pages, 3 figures, journal version, some references adde

Self-induced charge currents in electromagnetic materials, photon effective rest mass and some related topics

The contribution of self-induced charge currents of metamaterial media to photon effective rest mass is discussed in detail in the present paper. We concern ourselves with two kinds of photon effective rest mass, i.e., the frequency-dependent and frequency-independent effective rest mass. Based on these two definitions, we calculate the photon effective rest mass in the left-handed medium and the 2TDLM media, the latter of which is described by the so-called two time derivative Lorentz material (2TDLM) model. Additionally, we concentrate primarily on the torque, which is caused by the interaction between self-induced charge currents in dilute plasma (e.g., the secondary cosmic rays) and interstellar magnetic fields (ambient cosmic magnetic vector potentials), acting on the torsion balance of the rotating torsion balance experiment.Comment: 11 pages, Late

Vacuum properties of nonsymmetric gravity in de Sitter space

We consider quantum effects of a massive antisymmetric tensor field on the dynamics of de Sitter space-time. Our starting point is the most general, stable, linearized Lagrangian arising in nonsymmetric gravitational theories (NGTs), where part of the antisymmetric field mass is generated by the cosmological term. We construct a renormalization group (RG) improved effective action by integrating out one loop vacuum fluctuations of the antisymmetric tensor field and show that, in the limit when the RG scale goes to zero, the Hubble parameter -- and thus the effective cosmological constant -- relaxes rapidly to zero. We thus conclude that quantum loop effects in de Sitter space can dramatically change the infrared sector of the on-shell gravity, making the expansion rate insensitive to the original (bare) cosmological constant.Comment: 32 pages, 2 eps figure

Induced vacuum energy-momentum tensor in the background of a cosmic string

A massive scalar field is quantized in the background of a cosmic string which is generalized to a static flux-carrying codimension-2 brane in the locally flat multidimensional space-time. We find that the finite energy-momentum tensor is induced in the vacuum. The dependence of the tensor components on the brane flux and tension, as well as on the coupling to the space-time curvature scalar, is comprehensively analyzed. The tensor components are holomorphic functions of space dimension, decreasing exponentially with the distance from the brane. The case of the massless quantized scalar field is also considered, and the relevance of Bernoulli's polynomials of even order for this case is discussed.Comment: 21 pages, 2 figures; introductory part extended, references adde

Correlation Effects on Optical Conductivity of FeSi

Effects of electron correlation in FeSi are studied in terms of the two-band Hubbard model with the density of states obtained from the band calculation. Using the self-consistent second-order perturbation theory combined with the local approximation, the correlation effects are investigated on the density of states and the optical conductivity spectrum, which are found to reproduce the experiments done by Damascelli et al. semiquantitatively. It is also found that the peak at the gap edge shifts to lower energy region by correlation effects, as is seen in the experiments.Comment: 4 pages, 3 figure