Density-metric unimodular gravity: vacuum maximal symmetry

We have investigated the vacuum maximally symmetric solutions of recently proposed density-metric unimodular gravity theory,the results are widely different from inflationary senario.The exponential dependence on time in deSitter space is substiuted by a power law. Open space-times with non-zero cosmological constant are excluded in this theoryComment: 15 pages, no figures,stability section omitte

Biomolecular sensing using surface micromachined silicon plates

Micromachined sensors to detect surface stress changes associated with interactions between an immobilized chemically selective receptor and a target analyte are presented. The top isolated sensing surface of a free-standing silicon plate is prepared with a thin Au layer, followed by a covalent attachment of chemical or biomolecule forming a chemically-selective surface. Surface stress changes in air are measured capacitively due to the formation of an alkanethiol self-assembled monolayer (SAM). Detection of biomolecular binding in liquid samples is measured optically using the streptavidin-biotin complex and AM. tuberculosis antigen-antibody system used for clinical tuberculosis (TB) diagnosis

Monthly Newsletter

This is a personal letter to Kenneth Davis, AEC, concerning ORNL reactor activities. Topics covered include: HRP status; the gas-cooled system; molten fluorides; the ANP project; and maritime work

On causality, unitarity and perturbative expansions

We present a pedagogical case study how to combine micro-causality and unitarity based on a perturbative approach. The method we advocate constructs an analytic extrapolation of partial-wave scattering amplitudes that is constrained by the unitarity condition. Suitably constructed conformal mappings help to arrive at a systematic approximation of the scattering amplitude. The technique is illustrated at hand of a Yukawa interaction. The typical case of a superposition of strong short-range and weak long-range forces is investigated.Comment: 12 pages, 12 figure

Simple Mechanism of Softening Structure Functions at Low Transverse Momentum Region

The relevance of the dipole configurations of quarks in forming nucleus structure functions is discussed. It is shown that a radiation generated by dipole configurations while moving relativistically along their axises is described by distributions which are finite and infrared stable in low transverse momentum region. It is argued that there is an exponential transition to the perturbative regime of large transverse momenta and its power is defined by the distance between the dipole charges in its rest frame $m^{-1}_\pi$.Comment: 8 page

Scaling Behavior of Ricci Curvature at Short Distance near Two Dimensions

We study the renormalization of the Ricci curvature as an example of generally covariant operators in quantum gravity near two dimensions. We find that it scales with a definite scaling dimension at short distance. The Ricci curvature singularity at the big bang can be viewed as such a scaling phenomenon. The problem of the spacetime singularity may be resolved by the scale invariance of the spacetime at short distance.Comment: 9pages, LaTe

Neutral Pion Photoproduction on Nuclei in Baryon Chiral Perturbation Theory

Threshold neutral pion photoproduction on light nuclei is studied in the framework of baryon chiral perturbation theory. We obtain a general formula for the electric dipole amplitude in the special case of neutral pion photoproduction on a nucleus. To third order in small momenta, the amplitude is a sum of 2- and 3-body interactions with no undetermined parameters. With reasonable input from the single nucleon sector, our result for neutral pion photoproduction on the deuteron is in agreement with experiment.Comment: 24 pages, 4 uuencoded postscript figures, uses LaTex and epsf.tex. Added footnote and references. Minor changes in text and forma

Nonlinear Schroedinger Equations within the Nelson Quantization Picture

We present a class of nonlinear Schroedinger equations (NLSEs) describing, in the mean field approximation, systems of interacting particles. This class of NLSEs is obtained generalizing expediently the approach proposed in Ref. [G.K. Phys. Rev. A 55, 941 (1997)], where a classical system obeying to an exclusion-inclusion principle is quantized using the Nelson stochastic quantization. The new class of NLSEs is obtained starting from the most general nonlinear classical kinetics compatible with a constant diffusion coefficient D=\hbar/2m. Finally, in the case of s-stationary states, we propose a transformation which linearizes the NLSEs here proposed.Comment: 5 pages, (RevTeX4), to appear in Rep. Math. Phys. 51 (2003

Estimate of the Collins fragmentation function in a chiral invariant approach

We predict the features of the Collins function, which describes the fragmentation of a transversely polarized quark into an unpolarized hadron, by modeling the fragmentation process at a low energy scale. We use the chiral invariant approach of Manohar and Georgi, where constituent quarks and Goldstone bosons are considered as effective degrees of freedom in the non-perturbative regime of QCD. To test the approach we calculate the unpolarized fragmentation function and the transverse momentum distribution of a produced hadron, both of which are described reasonably well. In the case of semi-inclusive deep-inelastic scattering, our estimate of the Collins function in connection with the transversity distribution gives rise to a transverse single spin asymmetry of the order of 10%, supporting the idea of measuring the transversity distribution of the nucleon in this way. In the case of e+ e- annihilation into two hadrons, our model predicts a Collins azimuthal asymmetry of about 5%.Comment: 12 pages, 15 figures. Figs. 11-14 changed, minor changes in discussion, few typos fixed and some references added. Final version to appear in PR

Vortex Holography

We show that the Abelian Higgs field equations in the four dimensional anti de Sitter spacetime have a vortex line solution. This solution, which has cylindrical symmetry in AdS$_4$, is a generalization of the flat spacetime Nielsen-Olesen string. We show that the vortex induces a deficit angle in the AdS$_4$ spacetime that is proportional to its mass density. Using the AdS/CFT correspondence, we show that the mass density of the string is uniform and dual to the discontinuity of a logarithmic derivative of correlation function of the boundary scalar operator.Comment: LaTeX, 20 pages, 4 eps figures, references and two paragraphs added, to appear in Nucl. Phys.