7,024 research outputs found
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 is predicted to be a little
weaker than . 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 are measured in , d+Au and Au+Au
collisions at GeV . The nuclear modification factors in
d+Au collisions are presented. The 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 Term
We compute quadratically divergent supergravity one-loop effects on soft
supersymmetry-breaking parameters and the 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 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
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