Modular Cosmology

An exploratory study of the cosmology of moduli in string theory. Moduli are argued to be natural inflaton fields and lead to a robust inflationary cosmology in which inflation takes place at the top of domain walls. The amplitude of microwave background fluctuations constrains the dynamics responsible for inflation to take place at a higher scale than supersymmetry breaking. Models explaining this difference in scales and also preventing the dilaton from running to infinity are proposed. The problem of dilaton domination of the energy density of the universe is not resolved.Comment: harvmac, 37 pages, 3 figures as a separate uuencoded tar fil

Gasperini syndrome as clinical manifestation of pontine demyelination

The Gasperini syndrome is a very rare brainstem disease characterized by the typical combination of ipsilateral lesions of the cranial nerves V-VII and dissociated contralateral hemihypesthesia, whereas both contralateral and ipsilateral hypacusis was described. Since the first description in 1912, only a few cases of this crossed brainstem syndrome were published so far. Pontine infarction and bleedings were the reported causes of the syndrome. Here we report a 44-year-old man with the classical Gasperini syndrome due to pontine demyelination in multiple sclerosis. The clinical findings were correlated with changes on MRI. The present case shows that classical crossed brainstem syndromes are topological terms not invariably associated with brainstem ischemia in particular vascular areas and may contribute to the differential diagnosis of peripheral facial nerve palsy

Axion-Dilaton Cosmology and Dark Energy

We discuss a class of flat FRW cosmological models based on D=4 axion-dilaton gravity universally coupled to cosmological background fluids. In particular, we investigate the possibility of recurrent acceleration, which was recently shown to be generically realized in a wide class of axion-dilaton models, but in absence of cosmological background fluids. We observe that, once we impose the existence of radiation -and matter- dominated earlier stages of cosmic evolution, the axion-dilaton dynamics is altered significantly with respect to the case of pure axion-dilaton gravity. During the matter dominated epoch the scalar fields remain either frozen, due to the large expansion rate, or enter a cosmological scaling regime. In both cases, oscillations of the effective equation of state around the acceleration boundary value are impossible. Models which enter an oscillatory stage in the low redshift regime, on the other hand, are disfavored by observations. We also comment on the viability of the axion-dilaton system as a candidate for dynamical dark energy. In a certain subclass of models, an intermediate scaling regime is succeeded by eternal acceleration. We also briefly discuss the issue of dependence on initial conditions.Comment: 28 pages, 11 figure

Multidimensional cosmological models: cosmological and astrophysical implications and constraints

We investigate four-dimensional effective theories which are obtained by dimensional reduction of multidimensional cosmological models with factorizable geometry and consider the interaction between conformal excitations of the internal space (geometrical moduli excitations) and Abelian gauge fields. It is assumed that the internal space background can be stabilized by minima of an effective potential. The conformal excitations over such a background have the form of massive scalar fields (gravitational excitons) propagating in the external spacetime. We discuss cosmological and astrophysical implications of the interaction between gravexcitons and four-dimensional photons as well as constraints arising on multidimensional models of the type considered in our paper. In particular, we show that due to the experimental bounds on the variation of the fine structure constant, gravexcitons should decay before nucleosynthesis starts. For a successful nucleosynthesis the masses of the decaying gravexcitons should be m>10^4 GeV. Furthermore, we discuss the possible contribution of gravexcitons to UHECR. It is shown that, at energies of about 10^{20}eV, the decay length of gravexcitons with masses m>10^4 GeV is very small, but that for m <10^2 GeV it becomes much larger than the Greisen-Zatsepin-Kuzmin cut-off distance. Finally, we investigate the possibility for gravexciton-photon oscillations in strong magnetic fields of astrophysical objects. The corresponding estimates indicate that even the high magnetic field strengths of magnetars are not sufficient for an efficient and copious production of gravexcitons.Comment: 16 pages, LaTeX2e, minor changes, improved references, to appear in PR

Plasma heavy metal levels correlate with deregulated gene expression of detoxifying enzymes in osteoporotic patients

Heavy metal levels appear to be associated with low bone mineral density (BMD) and the consequent osteoporosis risk, but the relationship with the disease has not been clearly defined. The altered expression pattern of numerous genes, including detoxifying genes, seems to play a pivotal role in this context, leading to increased susceptibility to several diseases, including osteoporosis. The purpose of this study is to analyse circulating heavy metals levels and the expression of detoxifying genes in osteoporotic patients (OPs, n = 31), compared with healthy subjects (CTRs, n = 32). Heavy metals concentration in plasma samples was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and the subsequent expression analysis of NAD(P)H quinone dehydrogenase 1 (NQO1), Catalase (CAT), and Metallothionein 1E (MT1E) genes in Peripheral Blood Mononuclear Cells (PBMCs) was assessed by real-time polymerase chain reaction (qRT-PCR). Copper (Cu), mercury (Hg), molybdenum (Mo) and lead (Pb) were found to be significantly higher in the plasma of OPs compared to CTRs. Analysis of the expression levels of detoxifying genes showed a significant decrease in CAT and MT1E in OP group. In addition, Cu correlated positively with the expression levels of&nbsp;both CAT and MT1E in CTRs group and MT1E in OPs. This study shows an&nbsp;increased circulating&nbsp;concentration&nbsp;of certain metals combined with an altered&nbsp;expression pattern of detoxifying genes in OPs, highlighting a novel&nbsp;aspect to be&nbsp;investigated in order to better characterize the role of metals in&nbsp;the pathogenesis of osteoporosis

Test of Special Relativity and Equivalence principle from K Physics

A violation of Local Lorentz Invariance (VLI) and hence the special theory of relativity or a violation of equivalence principle (VEP) in the Kaon system can, in principle, induce oscillations between $K^0$ and $\bar{K}^0$. We construct a general formulation in which simultaneous pairwise diagonalization of mass, momemtum, weak or gravitational eigenstates is not assumed. %and the maximum attainable %velocities of the velocity eigenstates are different. We discuss this problem in a general way and point out that, as expected, the VEP and VLI contributions are indistinguishable. We then insist on the fact that VEP or VLI can occur even when CPT is conserved. A possible CP violation of the superweak type induced by VEP or VLI is introduced and discussed. We show that the general VEP mechanism (or the VLI mechanism, but not both simultaneously), with or without conserved CPT, could be clearly tested experimentally through the energy dependence of the $K_L-K_S$ mass difference and of $\eta_{+-}$, $\eta_{00}$, $\delta$. Constraints imposed by present experiments are calculated.Comment: Latex, 15 pages, 1 figure, version to appear in Phys. Rev.

Einstein and Brans-Dicke frames in multidimensional cosmology

Inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold M= M_0 x M_1 ...x M_n are investigated under dimensional reduction to a D_0-dimensional effective non-minimally coupled sigma-model which generalizes the familiar Brans-Dicke model. It is argued that the Einstein frame should be considered as the physical one. The general prescription for the Einstein frame reformulation of known solutions in the Brans-Dicke frame is given. As an example, the reformulation is demonstrated explicitly for the generalized Kasner solutions where it is shown that in the Einstein frame there are no solutions with inflation of the external space.Comment: 27 pages, Revte

Holographic bounds on the UV cutoff scale in inflationary cosmology

We discuss how holographic bounds can be applied to the quantum fluctuations of the inflaton. In general the holographic principle will lead to a bound on the UV cutoff scale of the effective theory of inflation, but it will depend on the coarse-graining prescription involved in calculating the entropy. We propose that the entanglement entropy is a natural measure of the entropy of the quantum perturbations, and show which kind of bound on the cutoff it leads to. Such bounds are related to whether the effects of new physics will show up in the CMB.Comment: 19 pages, 2 figures;(V3):Comments and references adde

On matching conditions for cosmological perturbations

We derive the matching conditions for cosmological perturbations in a Friedmann Universe where the equation of state undergoes a sharp jump, for instance as a result of a phase transition. The physics of the transition which is needed to follow the fate of the perturbations is clarified. We dissipate misleading statements made recently in the literature concerning the predictions of the primordial fluctuations from inflation and confirm standard results. Applications to string cosmology are considered.Comment: 20 pages, latex (revtex), no figure