Brans-Dicke theory: Jordan vs Einstein Frame

It is well known that, in contrast to general relativity, there are two conformally related frames, the Jordan frame and the Einstein frame, in which the Brans-Dicke theory, a prototype of generic scalar-tensor theory, can be formulated. There is a long standing debate on the physical equivalence of the formulations in these two different frames. It is shown here that gravitational deflection of light to second order accuracy may observationally distinguish the two versions of the Brans-Dicke theory.Comment: 10 pages, Accepted by Mod. Phys. Letts.

Experimental investigation of the fundamental modes of a collisionless plasma Final report, 10 Mar. 1964 - 31 Oct. 1967

Propagation of electron cyclotron waves and effects of low frequency noise in collisionless plasm

Compatibility of Einstein minimally coupled self interacting scalar field theory with the solar system tests of gravity

We examine the compatibility of the Einstein minimally coupled self-interacting scalar field theory with the local tests of gravity. We find that apart from the trivial case of the Schwarzschild-de Sitter solution with constant scalar field the theory does not admit any other static solution, which is consistent with the solar system tests of gravity.Comment: 6 pages, a part of the earlier version removed, final version accepeted by CQ

Gravitational lensing by a charged black hole of string theory

We study gravitational lensing by the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole of heterotic string theory and obtain the angular position and magnification of the relativistic images. Modeling the supermassive central object of the galaxy as a GMGHS black hole, we estimate the numerical values of different strong-lensing parameters. We find that there is no significant string effect present in the lensing observables in the strong-gravity scenario.Comment: 6 page

On static spherically symmetric solutions of the vacuum Brans-Dicke theory

It is shown that among the four classes of the static spherically symmetric solution of the vacuum Brans-Dicke theory of gravity only two are really independent. Further by matching exterior and interior (due to physically reasonable spherically symmetric matter source) scalar fields it is found that only Brans class I solution with certain restriction on solution parameters may represent exterior metric for a nonsingular massive object. The physical viability of the black hole nature of the solution is investigated. It is concluded that no physical black hole solution different from the Schwarzschild black hole is available in the Brans-Dicke theory.Comment: 15 pages, To be published in Gen. Rel. and Grav, typos in references correcte

Strong field gravitational lensing in scalar tensor theories

Strong field gravitational lensing in the Brans-Dicke theory has been studied. The deflection angle for photons passing very close to the photon sphere is estimated for the static spherically symmetric space-time of the theory and the position and magnification of the relativistic images are obtained. Modeling the super massive central object of the galaxy by the Brans-Dicke space-time, numerical values of different strong lensing observable are estimated. It is found that against the expectation there is no significant scalar field effect in the strong field observable lensing parameters. This observation raises question on the potentiality of the strong field lensing to discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio

Drosophila Argonaute-1 is critical for transcriptional cosuppression and heterochromatin formation

Argonaute-1 (Ago-1) plays a crucial role in gene regulation and genome stability via biogenesis of small non-coding RNAs. Two “Argonaute” family genes, piwi and Ago-2 in Drosophila are involved in multiple silencing mechanisms in the nucleus, transgene cosuppression, long-distant chromosome interaction, nuclear organization and heterochromatin formation. To investigate whether Ago-1 also plays a similar role, we have generated a series of Ago-1 mutations by excising P element, inserted in the Ago-1 promoter (Ago-1k08121). AGO-1 protein is distributed uniformly in the nucleus and cytosol in early embryos but accumulated predominantly in the cytoplasm during the gastrulation stage. Repeat induced silencing produced by the mini-white (mw) array and transcriptional cosuppression of non-homologous transgenes Adh-w/w-Adh was disrupted by Ago-1 mutation. These effects of Ago-1 are distict from its role in microRNA processing because Dicer-1, a critical enzyme for miRNA biogenesis, has no role on the above silencing. Reduction of AGO-1 protein dislodged the POLYCOMB, EZ (enhancer of zeste) and H3me3K27 binding at the cosuppressed Adh-w transgene insertion sites suggesting its role in Polycomb dependent cosuppression. An overall reduction of methylated histone H3me2K9 and H3me3K27 from the polytene nuclei precisely from the mw promoters was also found that leads to concomitant changes in the chromatin structure. These results suggest a prominent role of Ago-1 in chromatin organization and transgene silencing and demonstrate a critical link between transcriptional transgene cosuppression, heterochromatin formation and chromatin organization. We propose Drosophila Ago-1 as a multifunctional RNAi component that interconnects at least two unrelated events, chromatin organization in the nucleus and microRNA processing in the cytoplasm, which may be extended to the other systems

On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective String Theory in Einstein and Jordan Frames

Three new classes (II-IV) of solutions of the vacuum low energy effective string theory in four dimensions are derived. Wormhole solutions are investigated in those solutions including the class I case both in the Einstein and in the Jordan (string) frame. It turns out that, of the eight classes of solutions investigated (four in the Einstein frame and four in the corresponding string frame), massive Lorentzian traversable wormholes exist in five classes. Nontrivial massless limit exists only in class I Einstein frame solution while none at all exists in the string frame. An investigation of test scalar charge motion in the class I solution in the two frames is carried out by using the Plebanski-Sawicki theorem. A curious consequence is that the motion around the extremal zero (Keplerian) mass configuration leads, as a result of scalar-scalar interaction, to a new hypothetical "mass" that confines test scalar charges in bound orbits, but does not interact with neutral test particles.Comment: 18 page

Design and Test of a Forward Neutron Calorimeter for the ZEUS Experiment

A lead scintillator sandwich sampling calorimeter has been installed in the HERA tunnel 105.6 m from the central ZEUS detector in the proton beam direction. It is designed to measure the energy and scattering angle of neutrons produced in charge exchange ep collisions. Before installation the calorimeter was tested and calibrated in the H6 beam at CERN where 120 GeV electrons, muons, pions and protons were made incident on the calorimeter. In addition, the spectrum of fast neutrons from charge exchange proton-lucite collisions was measured. The design and construction of the calorimeter is described, and the results of the CERN test reported. Special attention is paid to the measurement of shower position, shower width, and the separation of electromagnetic showers from hadronic showers. The overall energy scale as determined from the energy spectrum of charge exchange neutrons is compared to that obtained from direct beam hadrons.Comment: 45 pages, 22 Encapsulated Postscript figures, submitted to Nuclear Instruments and Method