17,691 research outputs found
The D3/D7 Background and Flavor Dependence of Regge Trajectories
In the context of AdS/CFT with flavor, we consider the type IIB supergravity
solution corresponding to a fully localized D3/D7 intersection. We complete the
standard metric ansatz by providing an analytic expression for the warp factor,
under the assumption of a logarithmically running axion-dilaton. From the gauge
dual perspective, this behavior is related to the positive beta function of the
N=4, d=4 SU(N_c) super Yang-Mills gauge theory, coupled to N_f fundamental N=2
hypermultiplets. We comment on the existence of tadpoles and relate them to the
same gauge theory beta function. Next we consider a classical spinning string
configuration in the decoupling limit of the D3/D7 geometry and extract the
flavor (N_f) dependence of the associated meson Regge trajectory. Including the
backreaction of the D7-branes in the supergravity dual allows for going beyond
the quenched approximation on the dual gauge theory side.Comment: 26 pages, 5 figure
A simulation method for determining the optical response of highly complex photonic structures of biological origin
We present a method based on a time domain simulation of wave propagation
that allows studying the optical response of a broad range of dielectric
photonic structures. This method is particularly suitable for dealing with
complex biological structures. One of the main features of the proposed
approach is the simple and intuitive way of defining the setup and the photonic
structure to be simulated, which can be done by feeding the simulation with a
digital image of the structure. We also develop a set of techniques to process
the behavior of the evolving waves within the simulation. These techniques
include a direction filter, that permits decoupling of waves travelling
simultaneously in different directions, a dynamic differential absorber, to
cancel the waves reflected at the edges of the simulation space, a
multi-frequency excitation scheme based on a filter that allows decoupling
waves of different wavelengths travelling simultaneously, and a
near-to-far-field approach to evaluate the resulting wavefield outside the
simulation domain. We validate the code and, as an example, apply it to the
complex structure found in a microorganism called Diachea leucopoda, which
exhibits a multicolor iridescent appearance.Comment: 43 pages, 19 figure
Leptonic CP phases near the symmetric limit
The neutrino masses and mixings indicated by current neutrino oscillation
experiments suggest that the neutrino mass matrix possesses an approximate
exchange symmetry. In this study, we explore the neutrino parameter
space and show that if a small symmetry breaking is considered, the
Majorana phases must be unequal and non-zero independently of the neutrino
mass scale. Moreover, a small symmetry breaking favors
quasi-degenerate masses. We also show that Majorana phases are strongly
correlated with the Dirac violating phase. Within this framework, we
obtain robust predictions for the values of the Majorana phases when the
experimental indications for the Dirac phase are used.Comment: 13 pages, 3 figures. Version accepted for publication in PL
Macroscopic tunneling, decoherence and noise-induced activation
We study the effects of the environment at zero temperature on tunneling in
an open system described by a static double-well potential. We show that the
evolution of the system in an initial Schrodinger cat state, can be summarized
in terms of three main physical phenomena, namely decoherence, quantum
tunneling and noise-induced activation. Using large-scale numerical
simulations, we obtain a detailed picture of the main stages of the evolution
and of the relevant dynamical processesComment: Contribution to the Proceedings of DICE'0
An Experimental Study on the Heat Enhancement and the Bio-Heat Transfer Using Gold Macro Road and Ultrasound: A Potential Alternative to Kill Cancer Cells
We have previously proposed a method of treating solid tumors with a combination of gold macro-rods irradiated with ultrasound. Macro particle sized rods offer a greater circumferential treatment area over nanoparticle options. Experimental studies were conducted to investigate the heat enhancement and the bio-heat transfer to breast chicken using gold macro rod and ultrasound. An ultrasound, other than a focused ultrasound, may produce heat enough to cook a chicken breast up to about 1 cm diameter if a single gold rod is placed on the superficial tissue. Simulations and experimental results will provide the means to evaluate the treatment, to better design a patient-specific therapy to achieve maximum destruction of tumor and injury minimization of healthy tissue by controlling size, shape and location of gold seeds and ultrasound parameters
Investigating the relationship between predictability and imbalance in minimisation : a simulation study
Peer reviewedPublisher PD
Negative Magnetoresistance in Amorphous Indium Oxide Wires
We study magneto-transport properties of several amorphous Indium oxide
nanowires of different widths. The wires show superconducting transition at
zero magnetic field, but, there exist a finite resistance at the lowest
temperature. The broadening was explained by available phase slip
models. At low field, and far below the superconducting critical temperature,
the wires with diameter equal to or less than 100 nm, show negative
magnetoresistance (nMR). The magnitude of nMR and the crossover field are found
to be dependent on both temperature and the cross-sectional area. We find that
this intriguing behavior originates from the interplay between two field
dependent contributions.Comment: 11 pages, 7 figure
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