1,637 research outputs found
On the pulsating strings in Sasaki-Einstein spaces
We study the class of pulsating strings in AdS_5 x Y^{p,q} and AdS_5 x
L^{p,q,r}. Using a generalized ansatz for pulsating string configurations, we
find new solutions for this class in terms of Heun functions, and derive the
particular case of AdS_5 x T^{1,1}, which was analyzed in arXiv:1006.1539
[hep-th]. Unfortunately, Heun functions are still little studied, and we are
not able to quantize the theory quasi-classically and obtain the first
corrections to the energy. The latter, due to AdS/CFT correspondence, is
supposed to give the anomalous dimensions of operators of the gauge theory dual
N=1 superconformal field theory.Comment: 9 pages, talk given at the 2nd Int. Conference AMiTaNS, 21-26 June
2010, Sozopol, Bulgaria, organized by EAC (Euro-American Consortium) for
Promoting AMiTaNS, to appear in the Proceedings of 2nd Int. Conference
AMiTaN
Conformational effects on the Circular Dichroism of Human Carbonic Anhydrase II: a multilevel computational study
Circular Dichroism (CD) spectroscopy is a powerful method for investigating conformational changes in proteins and therefore has numerous applications in structural and molecular biology. Here a computational investigation of the CD spectrum of the Human Carbonic Anhydrase II (HCAII), with main focus on the near-UV CD spectra of the wild-type enzyme and it seven tryptophan mutant forms, is presented and compared to experimental studies. Multilevel computational methods (Molecular Dynamics, Semiempirical Quantum Mechanics, Time-Dependent Density Functional Theory) were applied in order to gain insight into the mechanisms of interaction between the aromatic chromophores within the protein environment and understand how the conformational flexibility of the protein influences these mechanisms. The analysis suggests that combining CD semi empirical calculations, crystal structures and molecular dynamics (MD) could help in achieving a better agreement between the computed and experimental protein spectra and provide some unique insight into the dynamic nature of the mechanisms of chromophore interactions
Exploring quantum non-locality with de Broglie-Bohm trajectories
Here in this paper, it is shown how the quantum nonlocality reshapes
probability distributions of quantum trajectories in configuration space. By
variationally minimizing the ground state energy of helium atom we show that
there exists an optimal nonlocal quantum correlation length which also
minimizes the mean integrated square error of the smooth trajectory ensemble
with respect to the exact many-body wave function. The nonlocal quantum
correlation length can be used for studies of both static and driven many-body
quantum systems.Comment: 19 pages, 5 figure
Quantum trajectory perspective of atom-field interaction in attosecond time scale
Here the ionization and high harmonic generation in Hydrogen and Helium by
using quantum (hydrodynamic) trajectories is analyzed theoretically. The
quantum trajectories allow a self-contained treatment of the electron exchange
and correlation effects without introducing ad hoc potentials into the
Schrodinger equation. Our approach predicts the correct high harmonic spectra
and the attosecond pulses generated by the Helium atom beyond the single active
electron approximation. It can be used to study complex multi-electron systems
and their interaction with laser field of both high and low intensity.Comment: 8 pages, 4 figure
Weak electricity of the Nucleon in the Chiral Quark-Soliton Model
The induced pseudotensor constant (weak electricity) of the nucleon is
calculated in the framework of the chiral quark soliton model. This quantity
originates from the G-parity violation and hence is proportional to .
We obtain for a value of .Comment: The final version. Accepted for publication in Phys. Rev.
Cutting and Shuffling a Line Segment: Mixing by Interval Exchange Transformations
We present a computational study of finite-time mixing of a line segment by
cutting and shuffling. A family of one-dimensional interval exchange
transformations is constructed as a model system in which to study these types
of mixing processes. Illustrative examples of the mixing behaviors, including
pathological cases that violate the assumptions of the known governing theorems
and lead to poor mixing, are shown. Since the mathematical theory applies as
the number of iterations of the map goes to infinity, we introduce practical
measures of mixing (the percent unmixed and the number of intermaterial
interfaces) that can be computed over given (finite) numbers of iterations. We
find that good mixing can be achieved after a finite number of iterations of a
one-dimensional cutting and shuffling map, even though such a map cannot be
considered chaotic in the usual sense and/or it may not fulfill the conditions
of the ergodic theorems for interval exchange transformations. Specifically,
good shuffling can occur with only six or seven intervals of roughly the same
length, as long as the rearrangement order is an irreducible permutation. This
study has implications for a number of mixing processes in which
discontinuities arise either by construction or due to the underlying physics.Comment: 21 pages, 10 figures, ws-ijbc class; accepted for publication in
International Journal of Bifurcation and Chao
Attosecond time-scale intra-atomic phase matching of high harmonic generation
Includes bibliographical references (page 5461).Using a model of high-harmonic generation that couples a fully quantum calculation with a semi-classical electron trajectory picture, we show that a new type of phase matching is possible when an atom is driven by an optimal optical waveform. For an optimized laser pulse shape, strong constructive interference is obtained in the frequency domain between emissions from different electron trajectories, thereby selectively enhancing a particular harmonic order. This work demonstrates that coherent control in the strong-field regime is possible by adjusting the peaks of a laser field on an attosecond time scale
Stretching and folding versus cutting and shuffling: An illustrated perspective on mixing and deformations of continua
We compare and contrast two types of deformations inspired by mixing
applications -- one from the mixing of fluids (stretching and folding), the
other from the mixing of granular matter (cutting and shuffling). The
connection between mechanics and dynamical systems is discussed in the context
of the kinematics of deformation, emphasizing the equivalence between stretches
and Lyapunov exponents. The stretching and folding motion exemplified by the
baker's map is shown to give rise to a dynamical system with a positive
Lyapunov exponent, the hallmark of chaotic mixing. On the other hand, cutting
and shuffling does not stretch. When an interval exchange transformation is
used as the basis for cutting and shuffling, we establish that all of the map's
Lyapunov exponents are zero. Mixing, as quantified by the interfacial area per
unit volume, is shown to be exponentially fast when there is stretching and
folding, but linear when there is only cutting and shuffling. We also discuss
how a simple computational approach can discern stretching in discrete data.Comment: REVTeX 4.1, 9 pages, 3 figures; v2 corrects some misprints. The
following article appeared in the American Journal of Physics and may be
found at http://ajp.aapt.org/resource/1/ajpias/v79/i4/p359_s1 . Copyright
2011 American Association of Physics Teachers. This article may be downloaded
for personal use only. Any other use requires prior permission of the author
and the AAP
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