Comment on ``Inflation and flat directions in modular invariant superstring effective theories''

The inflation model of Gaillard, Lyth and Murayama is revisited, with a systematic scan of the parameter space for dilaton stabilization during inflation.Comment: 7 pages, 2 figure

The Standard Model of Particle Physics

Particle physics has evolved a coherent model that characterizes forces and particles at the most elementary level. This Standard Model, built from many theoretical and experimental studies, is in excellent accord with almost all current data. However, there are many hints that it is but an approximation to a yet more fundamental theory. We trace the development of the Standard Model and indicate the reasons for believing that it is incomplete.Comment: 25 pages, 17 figures; accepted for publication in Rev. Mod. Physics (APS centenary issue

Constitutive relations, off shell duality rotations and the hypergeometric form of Born-Infeld theory

We review equivalent formulations of nonlinear and higher derivatives theories of electromagnetism exhibiting electric-magnetic duality rotations symmetry. We study in particular on shell and off shell formulations of this symmetry, at the level of action functionals as well as of equations of motion. We prove the conjecture that the action functional leading to Born-Infeld nonlinear electromagnetism, that is duality rotation invariant off shell and that is known to be a root of an algebraic equation of fourth order, is a hypergeometric function.Comment: 20 pages. Contribution to the proceedings of the conference BUDS2013, Frascat

Application of the operator product expansion to the short distance behavior of nuclear potentials

We investigate the short distance behavior of nucleon-nucleon (NN) potentials defined through Bethe-Salpeter wave functions, by perturbatively calculating anomalous dimensions of 6-quark operators in QCD. Thanks to the asymptotic freedom of QCD, 1-loop computations give certain exact results for the potentials in the zero distance limit. In particular the functional form of the S-state central NN potential at short distance $r$ is predicted to be a little weaker than $r^{-2}$. On the other hand, due to the intriguing character of the anomalous dimension spectrum, perturbative considerations alone can not determine whether this potential is repulsive or attractive at short distances. A crude estimation suggests that the force at short distance is repulsive, as found numerically in lattice QCD. A similar behavior is found for the tensor potential.Comment: 40 pages, no figure

Baryonic Resonance Studies with STAR

Yields and spectra of $\Sigma(1385)$ are measured in $p+p$, d+Au and Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV . The nuclear modification factors in d+Au collisions are presented. The $p_{T}$ dependent medium effects are investigated via the nuclear modification factors. The implications of these results on various models are discussed.Comment: Strange Quark Matter 2006 Conference Talk Proceeding

Event by Event fluctuation in K/pi ratio at RHIC

We present the preliminary results from our analysis of event by event fluctuation in K/pi ratio in Au+Au collision at \sqrt s_{NN} = 200 GeV and at 62.4 GeV using STAR detector at RHIC. Two different methods have been used to extract the strength of dynamical fluctuation and the centrality dependence of that. The results from the study of energy and centrality dependence of the dynamical fluctuation are presented. From the excitation function it is seen that at two RHIC energies the measure of dynamical fluctuation is constant with values very close to that at 12.3 GeV at SPS. The dynamical fluctuation is found to be positive and decreasing with increasing centrality at RHIC. The results are compared with HIJING model calculation with jets. Results from HIJING are found to be very close to data from central collisions whereas it over predicts the data for peripheral events.Comment: 4 pages, 3 figures, for ICPAQGP - 2005 (Recalculated the errors shown in Fig 2 and Table 1

Three-way electrical gating characteristics of metallic Y-junction carbon nanotubes

Y-junction based carbon nanotube (CNT) transistors exhibit interesting switching behaviors, and have the structural advantage that the electrical gate for current modulation can be formed by any of the three constituent branches. In this letter, we report on the gating characteristics of metallic Y-CNT morphologies. By measuring the output conductance and transconductance we conclude that the efficiency and gain depend on the branch diameter and is electric field controlled. Based on these principles, we propose a design for a Y-junction based CNT switching device, with tunable electrical properties

New approach to nonlinear electrodynamics: dualities as symmetries of interaction

We elaborate on the duality-symmetric nonlinear electrodynamics in a new formulation with auxiliary tensor fields. The Maxwell field strength appears only in bilinear terms of the corresponding generic Lagrangian, while the self-interaction is presented by a function E depending on the auxiliary fields. Two types of dualities inherent in the nonlinear electrodynamics models admit a simple off-shell characterization in terms of this function. In the standard formulation, the continuous U(1) duality symmetry is nonlinearly realized on the Maxwell field strength. In the new setting, the same symmetry acts as linear U(1) transformations of the auxiliary field variables. The nonlinear U(1) duality condition proves to be equivalent to the linear U(1) invariance of the self-interaction E. The discrete self-duality (or self-duality by Legendre transformation) amounts to a weaker reflection symmetry of E. For a class of duality- symmetric Lagrangians we introduce an alternative representation with the auxiliary scalar field and find new explicit examples of such systems.Comment: Latex file, 21 page

Supergravity Radiative Effects on Soft Terms and the μ\mu Term

We compute quadratically divergent supergravity one-loop effects on soft supersymmetry-breaking parameters and the $\mu$ term in generic hidden sector supergravity models. These effects can significantly modify the matching condition for soft parameters at the Planck scale and also provide several new sources of the $\mu$ term which are naturally of order the weak scale. We also discuss some phenomenological implications of these effects, particularly the violation of the scalar mass universality which may lead to dangerous FCNC phenomena, and apply the results to superstring effective supergravity models.Comment: 12 pages, REVTEX. One reference is adde