We propose an experiment for creating quantum superposition states involving of the order of 10(14) atoms via the interaction of a single photon with a tiny mirror. This mirror, mounted on a high-quality mechanical oscillator, is part of a high-finesse optical cavity which forms one arm of a Michelson interferometer. By observing the interference of the photon only, one can study the creation and decoherence of superpositions involving the mirror. A detailed analysis of the requirements shows that the experiment is within reach using a combination of state-of-the-art technologies.

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Towards Quantum Superpositions of a Mirror

We review the properties of Galactic binaries containing two compact objects, as derived by means of population synthesis. Using this information we calculate the gravitational wave signal of these binaries. At frequencies below f < 2 mHz the double white dwarf population forms an unresolved background for the low- frequency gravitational wave detector LISA. Above this limit some few thousand double white dwarfs and few tens of binaries containing neutron stars will be resolved. Of the resolved double white dwarfs500 have a total mass above the Chandrasekhar limit. About95 of these have a measurable frequency change allowing a determination of their chirp mass. We discuss the properties of the resolved systems.

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The gravitational wave signal from the Galactic disk population of binaries containing two compact objects.

We study a holographic model of a relativistic quantum system with a global U(1) symmetry, at nonzero temperature and density. When the temperature falls below a critical value, we find a second-order superfluid phase transition with mean-field critical exponents. In the symmetry-broken phase, we determine the speed of second sound as a function of temperature. As the velocity of the superfluid component relative to the normal component increases, the superfluid transition goes through a tricritical point and becomes first order.

Holographic model of superfluidity

The Lorentz covariant theory of the propagation of light in the (weak) gravitational fields of N-body systems consisting of arbitrarily moving pointlike bodies with constant masses ${m}_{a}$ $(a=1,2,\dots{},N)$ is constructed. The theory is based on the Li\'enard-Wiechert representation of the metric tensor which describes a retarded type solution of the gravitational field equations. A new approach for integrating the equations of motion of light particles (photons) depending on the retarded time argument is invented. Its application in the first post-Minkowskian approximation, which is linear with respect to the universal gravitational constant G makes it evident that the equations of light propagation admit to be integrated straightforwardly by quadratures. Explicit expressions for the trajectory of a light ray and its tangent vector are obtained in algebraically closed form in terms of functionals of retarded time. General expressions for the relativistic time delay, the angle of light deflection, and the gravitational shift of electromagnetic frequency are derived in the form of instantaneous functions of retarded time. They generalize previously known results for the case of static or uniformly moving bodies. The most important applications of the theory to relativistic astrophysics and astrometry are given. They include a discussion of the velocity-dependent terms in the gravitational lens equation, the Shapiro time delay in binary pulsars, gravitational Doppler shift, and a precise theoretical formulation of the general relativistic algorithms of data processing of radio and optical astrometric measurements made in the nonstationary gravitational field of the solar system. Finally, proposals for future theoretical work being important for astrophysical applications are formulated.

Lorentz covariant theory of light propagation in gravitational fields of arbitrary moving bodies

A large family of solutions, representing, ingeneral, spherically symmetric Type II fluid, ispresented, which includes most of the known solutions tothe Einstein field equations, such as, the monopole-de Sitter-charged Vaidya ones

Generalized Vaidya Solutions

A Random Walk in Relativity and Cosmology

COMPARED to black holes, their time-reversed versions, white holes have attracted little attention from theoreticians. Here we point out possible ways in which white holes may be useful to high energy astrophysics.

Naresh Dadhich

Papers

A Random Walk in Relativity and Cosmology

High energy radiation from white holes

Gravitation and Relativity: At the turn of the Millennium