Search for large extra dimensions in dielectron and diphoton production

We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.     

Electrical excitation of surface plasmons

We exploit a plasmon mediated two-step momentum down-conversion scheme to convert low-energy tunneling electrons into propagating photons. Surface plasmon polaritons (SPPs) propagating along an extended gold nanowire are excited on one end by low-energy electron tunneling and are then converted to free-propagating photons at the other end. The separation of excitation and outcoupling proves that tunneling electrons excite gap plasmons that subsequently couple to propagating plasmons. Our work shows that electron tunneling provides a nonoptical, voltage-controlled, and low-energy pathway for launching SPPs in nanostructures, such as plasmonic waveguides.     

Reaction diffusion equation in the ultra cold coexisting atomic and molecular condensates and the importance of Feshbach interaction

We consider a gas of bosonic atoms near a Feshbach resonance. The dynamics of the atomic and molecular condensates can be described in the limit of small fluctuations by a set of coupled nonlinear Gross Piteaviskii equations. In the case of a strong atom-molecule conversion, the system has an integral motion for the spatially uniform solutions which exhibits temporal oscillation. The possible consequence of this oscillation may be the existence of Josephson like current in the condensates which has been investigated.     

Hydraulic jump in one-dimensional flow

In the presence of viscosity the hydraulic jump in one dimension is seen to be a first-order transition. A scaling relation for the position of the jump has been determined by applying an averaging technique on the stationary hydrodynamic equations. This gives a linear height profile before the jump, as well as a clear dependence of the magnitude of the jump on the outer boundary condition. The importance of viscosity in the jump formation has been convincingly established, and its physical basis has been understood by a time-dependent analysis of the flow equations. In doing so, a very close correspondence has been revealed between a perturbation equation for the flow rate and the metric of an acoustic white hole. We finally provide experimental support for our heuristically developed theory.     

Pattern formation in liquid crystals far from equilibrium

We have theoretically investigated the growth of the droplets of the nematic phase from supercooled isotropic phase of a liquid crystal. We have also suggested new experiments for testing our predictions in the early time regime.     

The Electric Dipole Moment of the CO2–CO van der Waals Complex

Radiofrequency transitions withinK= 2 asymmetry doublets have been observed for the CO₂–CO van der Waals complex. A Stark effect measurement on theJ= 2,K= 2 transition provides an electric dipole moment of μ = 0.2493(1) D. Combining this result with the permanent moment of CO, μ_CO= 0.1098 D, gives a change of moment on complex formation of Δμ = 0.140 D. The sign of Δμ is such that the CO end of the complex is more positive than CO₂. The origin of Δμ should not be attributed to any single mechanism, and several different contributions to Δμ are discussed.     

Polytope Games

Starting from the definition of a bimatrix game, we restrict the pair of strategy sets jointly, not independently. Thus, we have a set , which is the set of all feasible strategy pairs. We pose the question of whether a Nash equilibrium exists, in that no player can obtain a higher payoff by deviating. We answer this question affirmatively for a very general case, imposing a minimum of conditions on the restricted sets and the payoff. Next, we concentrate on a special class of restricted games, the polytope bimatrix game, where the restrictions are linear and the payoff functions are bilinear. Further, we show how the polytope bimatrix game is a generalization of the bimatrix game. We give an algorithm for solving such a polytope bimatrix game; finally, we discuss refinements to the equilibrium point concept where we generalize results from the theory of bimatrix games.     

Reissert compound studies. XXXVI. Observations on 1,7-, 4,6-, 4,7-, and 1,10-phenanthrolines

Reissert compounds have been prepared from 1,7-, 4,6-, and 4,7-phenanthrolines. In the case of 4,7-phenanthroline, both mono- and di-Reissert compounds have been prepared. A number of Reissert analogs have also been prepared in this series. 1,10-Phenanthroline fails to give a Reissert compound.     

Reissert compound studies. XXXVII. Attempts to form reissert compounds from quinazoline and cinnoline

Reaction of quinazoline with trimethylsilyl cyanide and benzoyl chloride gave 2,4-dicyano-1,3-dibenzoyl-1,2,3,4-tetrahydroquinazoline as the major product. This compound undergoes monoalkylation with methyl iodide in the presence of sodium hydride. Reaction of cinnoline with trimethylsilyl cyanide and benzoyl chloride gave 1,2-dibenzoyl-4-cyano-1,2-dihydrocinnoline.     

A trade-off between collision probability and key size in universal hashing using polynomials

Let \mathbbF{\mathbb{F}} be a finite field and suppose that a single element of \mathbbF{\mathbb{F}} is used as an authenticator (or tag). Further, suppose that any message consists of at most L elements of \mathbbF{\mathbb{F}}. For this setting, usual polynomial based universal hashing achieves a collision bound of (L-1)/|\mathbbF|{(L-1)/|\mathbb{F}|} using a single element of \mathbbF{\mathbb{F}} as the key. The well-known multi-linear hashing achieves a collision bound of 1/|\mathbbF|{1/|\mathbb{F}|} using L elements of \mathbbF{\mathbb{F}} as the key. In this work, we present a new universal hash function which achieves a collision bound of mélog_m Lù/|\mathbbF|, m 3 2{m\lceil\log_m L\rceil/|\mathbb{F}|, m\geq 2}, using 1+élog_m Lù{1+\lceil\log_m L\rceil} elements of \mathbbF{\mathbb{F}} as the key. This provides a new trade-off between key size and collision probability for universal hash functions.