386 research outputs found
Simplest cosmological model with the scalar field II. Influence of cosmological constant
Continuing the investigation of the simplest cosmological model with the
massive real scalar non-interacting inflaton field minimally coupled to gravity
we study an influence of the cosmological constant on the behaviour of
trajectories in closed minisuperspace Friedmann-Robertson-Walker model. The
transition from chaotic to regular behaviour for large values of cosmological
constant is discussed. Combining numerical calculations with qualitative
analysis both in configuration and phase space we present a convenient
classification of trajectories.Comment: 12 pages with 2 gif figures and 2 eps figures, mprocl.sty, To appear
in International Journal of Modern Physics
Reduction without reduction: Adding KK-monopoles to five dimensional stationary axisymmetric solutions
We present a general method to add KK-monopole charge to any asymptotically
flat stationary axisymmetric solution of five dimensional General Relativity.
The technique exploits the underlying SL(3,R) invariance of the system by
identifying a particular element of the symmetry group which changes the
asymptotic boundary condition and adds KK-monopole charge. Furthermore, we
develop a set of technical tools which allow us to apply the SL(3,R)
transformations to solutions produced by the Inverse Scattering method. As an
example of our methods, we construct the exact solution describing a static
black ring carrying KK-monopole charge.Comment: 36 pages, 3 figures, LaTeX, minor typos fixe
Polarization ququarts
We discuss the concept of polarization states of four-dimensional quantum
systems based on frequency non-degenerate biphoton field. Several quantum
tomography protocols were developed and implemented for measurement of an
arbitrary state of ququart. A simple method that does not rely on
interferometric technique is used to generate and measure the sequence of
states that can be used for quantum communication purposes.Comment: 13 pages, 10 figure
Predicting gene promoter methylation in non-small-cell lung cancer by evaluating sputum and serum
The use of 5-methylcytosine demethylating agents in conjunction with inhibitors of histone deacetylation may offer a new therapeutic strategy for lung cancer. Monitoring the efficacy of gene demethylating treatment directly within the tumour may be difficult due to tumour location. This study determined the positive and negative predictive values of sputum and serum for detecting gene methylation in primary lung cancer. A panel of eight genes was evaluated by comparing methylation detected in the primary tumour biopsy to serum and sputum obtained from 72 patients with Stage III lung cancer. The prevalence for methylation of the eight genes in sputum (21–43%) approximated to that seen in tumours, but was 0.7–4.3-fold greater than detected in serum. Sputum was superior to serum in classifying the methylation status of genes in the tumour biopsy. The positive predictive value of the top four genes (p16, DAPK, PAX5 β, and GATA5) was 44–72% with a negative predictive value for these genes ⩾70%. The highest specificity was seen for the p16 gene, and this was associated with a odds ratio of six for methylation in the tumour when this gene was methylated in sputum. In contrast, for serum, the individual sensitivity for all genes was 6–27%. Evaluating the combined effect of methylation of at least one of the four most significant genes in sputum increased the positive predictive value to 86%. These studies demonstrate that sputum can be used effectively as a surrogate for tumour tissue to predict the methylation status of advanced lung cancer where biopsy is not feasible
On the gravitational field of static and stationary axial symmetric bodies with multi-polar structure
We give a physical interpretation to the multi-polar Erez-Rozen-Quevedo
solution of the Einstein Equations in terms of bars. We find that each
multi-pole correspond to the Newtonian potential of a bar with linear density
proportional to a Legendre Polynomial. We use this fact to find an integral
representation of the function. These integral representations are
used in the context of the inverse scattering method to find solutions
associated to one or more rotating bodies each one with their own multi-polar
structure.Comment: To be published in Classical and Quantum Gravit
Hyperbolic billiards of pure D=4 supergravities
We compute the billiards that emerge in the Belinskii-Khalatnikov-Lifshitz
(BKL) limit for all pure supergravities in D=4 spacetime dimensions, as well as
for D=4, N=4 supergravities coupled to k (N=4) Maxwell supermultiplets. We find
that just as for the cases N=0 and N=8 investigated previously, these billiards
can be identified with the fundamental Weyl chambers of hyperbolic Kac-Moody
algebras. Hence, the dynamics is chaotic in the BKL limit. A new feature
arises, however, which is that the relevant Kac-Moody algebra can be the
Lorentzian extension of a twisted affine Kac-Moody algebra, while the N=0 and
N=8 cases are untwisted. This occurs for N=5, N=3 and N=2. An understanding of
this property is provided by showing that the data relevant for determining the
billiards are the restricted root system and the maximal split subalgebra of
the finite-dimensional real symmetry algebra characterizing the toroidal
reduction to D=3 spacetime dimensions. To summarize: split symmetry controls
chaos.Comment: 21 page
Two Kerr black holes with axisymmetric spins: An improved Newtonian model for the head-on collision and gravitational radiation
We present a semi-analytical approach to the interaction of two (originally)
Kerr black holes through a head-on collision process. An expression for the
rate of emission of gravitational radiation is derived from an exact solution
to the Einstein's field equations. The total amount of gravitational radiation
emitted in the process is calculated and compared to current numerical
investigations. We find that the spin-spin interaction increases the emission
of gravitational wave energy up to 0.2% of the total rest mass. We discuss also
the possibility of spin-exchange between the holes.Comment: 8 pages, RevTeX, 2 figures, psbox macro include
Mass-Inflation in Dynamical Gravitational Collapse of a Charged Scalar-Field
We study the inner-structure of a charged black-hole which is formed from the
gravitational collapse of a self-gravitating charged scalar-field. Starting
with a regular spacetime, we follow the evolution through the formation of an
apparent horizon, a Cauchy horizon and a final central singularity. We find a
null, weak, mass-inflation singularity along the Cauchy horizon, which is a
precursor of a strong, spacelike singularity along the hypersurface.Comment: Latex, 13 pages including 4 figures, Revtex.st
Clarifying Inflation Models: the Precise Inflationary Potential from Effective Field Theory and the WMAP data
We clarify inflaton models by considering them as effective field theories in
the Ginzburg-Landau spirit.In this new approach, the precise form of the
inflationary potential is constructed from the present WMAP data, and a useful
scheme is prepared to confront with the forthcoming data. In this approach, the
WMAP statement excluding the pure phi^4 potential implies the presence of an
inflaton mass term at the scale m sim 10^{13}GeV. Chaotic, new and hybrid
inflation is studied in an unified way. In all cases the inflaton potential
takes the form V(phi) = m^2 M_{Pl}^2 v(phi/M_{Pl}), where all coefficients in
the polynomial v(x) are of order one. If such potential corresponds to super
symmetry breaking, the susy breaking scale is sqrt{m M_{Pl}} \sim 10^{16}GeV
which turns to coincide with the GUT scale. The inflaton mass is therefore
given by a see-saw formula m sim M_{GUT}^2/M_{Pl}. The observables turn to be
two valued functions: one branch corresponds to new inflation and the other to
chaotic inflation,the branch point being the pure quadratic potential.For red
tilt spectrum, the potential which fits the best the present data and which
best prepares the way for the forthcoming data is a trinomial polynomial
withnegative quadratic term (new inflation).For blue tilt spectrum, hybrid
inflation turns to be the best choice. In both cases we find a formula relating
the inflaton mass with the ratio r of tensor/scalar perturbations and the
spectral index ns of scalar perturbations: 10^6 m/M_{Pl}= 127 sqrt{r|1-n_s|}
;(the coefficient 127 follows from the WMAP amplitude.Implications for string
theory are discussed.Comment: LaTeX, 33 pages, 24 .ps figures. Improved version published in Phys
Rev
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