6,217 research outputs found
Constrained Molecular Dynamics II: a N-body approach to nuclear systems
In this work we illustrate the basic development of the constrained molecular
dynamics applied to the N-body problem in nuclear physics. The heavy
computational taskes related to quantum effects, to the presence of the "hard
core" repulsive interaction have been worked out by defining a set of
transformations based on the concept of impulsive forces. In particular in the
implemented version II of the Constrained Molecular Dynamics model the problem
related to the non conservation of the total angular momentum has been solved.
This problem can affect others semiclassical microscopic approaches as due to
the "hard core" repulsive interaction or to the use of stochastic forces. The
effect of the restored conservation law on the fusion cross section for
40Ca+40Ca system is also briefly discussed.Comment: Tex version 3.1459 (Web2C 7.3.1);main text+fig.cap in .tex 13 page;
+4 figures .ps;the order and the numerical label of the figure files reflect
the figure numbers in the main tex and captions, Submited to Journal of
computational physic
Searching for continuous gravitational wave signals: the hierarchical Hough transform algorithm
It is well known that matched filtering techniques cannot be applied for
searching extensive parameter space volumes for continuous gravitational wave
signals. This is the reason why alternative strategies are being pursued.
Hierarchical strategies are best at investigating a large parameter space when
there exist computational power constraints. Algorithms of this kind are being
implemented by all the groups that are developing software for analyzing the
data of the gravitational wave detectors that will come online in the next
years. In this talk we will report about the hierarchical Hough transform
method that the GEO 600 data analysis team at the Albert Einstein Institute is
developing. The three step hierarchical algorithm has been described elsewhere.
In this talk we will focus on some of the implementational aspects we are
currently concerned with.Comment: 9 pages, 1 figure. To appear in the proceedings of the conference
``Gravitational waves: a challenge to theoretical astrophysics'', (June 5-9
2000, Trieste), ICTP Lecture Notes Serie
Analytical continuation from imaginary to real chemical potential in 2-color QCD under scrutiny
The method of analytical continuation from imaginary to real chemical
potential is tested in 2-color QCD. In comparison to previous studies in the
same theory, an exact updating algorithm is used and simulations are performed
closer to the thermodynamic limit. It is shown that the method considerably
improves if suitable functions are used to interpolate data with imaginary
chemical potential.Comment: 7 pages, 5 figures, Lattice 2006 (High Temperature and Density
The critical line of QCD with four degenerate quarks
We determine the pseudo-critical couplings at imaginary chemical potentials
by high-statistics Monte Carlo simulations of QCD with four degenerate quarks
at non-zero temperature and baryon density by the method of analytic
continuationan. We reveal deviations from the simple quadratic dependence on
the chemical potential visible in earlier works on the same subject. Finally,
we discuss the implications of our findings for the shape of the
pseudo-critical line at real chemical potential, comparing different possible
extrapolations.Comment: 7 pages, 7 figures, talk presented at the XXVIII International
Symposium on Lattice Field Theory, June 14-19, 2010, Villasimius, Sardinia,
Ital
Metal-Insulator Transition Tuned by External Gates in Hall Systems with Constrictions
The nature of a metal-insulator transition tuned by external gates in quantum
Hall (QH) systems with point constrictions, as reported in recent experiments
of Roddaro et al [1], is examined. We attribute this phenomenon to a splitting
of the integer edge into conducting and insulating stripes, the latter wide
enough to allow for the stability of the edge structure. Inter-channel impurity
scattering and inter-channel Coulomb interactions do not destabilize this
picture.Comment: 4 pages, 6 figure
Mass gap in the 2D O(3) non-linear sigma model with a theta=pi term
By analytic continuation to real theta of data obtained from numerical
simulation at imaginary theta we study the Haldane conjecture and show that the
O(3) non-linear sigma model with a theta term in 2 dimensions becomes massless
at theta=3.10(5). A modified cluster algorithm has been introduced to simulate
the model with imaginary theta. Two different definitions of the topological
charge on the lattice have been used; one of them needs renormalization to
match the continuum operator. Our work also offers a successful test for
numerical methods based on analytic continuation.Comment: Latex file, 4 pages. To appear in PRD; it contains the justification
of analicity, more details about the fits, more references, et
Random template banks and relaxed lattice coverings
Template-based searches for gravitational waves are often limited by the
computational cost associated with searching large parameter spaces. The study
of efficient template banks, in the sense of using the smallest number of
templates, is therefore of great practical interest. The "traditional" approach
to template-bank construction requires every point in parameter space to be
covered by at least one template, which rapidly becomes inefficient at higher
dimensions. Here we study an alternative approach, where any point in parameter
space is covered only with a given probability < 1. We find that by giving up
complete coverage in this way, large reductions in the number of templates are
possible, especially at higher dimensions. The prime examples studied here are
"random template banks", in which templates are placed randomly with uniform
probability over the parameter space. In addition to its obvious simplicity,
this method turns out to be surprisingly efficient. We analyze the statistical
properties of such random template banks, and compare their efficiency to
traditional lattice coverings. We further study "relaxed" lattice coverings
(using Zn and An* lattices), which similarly cover any signal location only
with probability < 1. The relaxed An* lattice is found to yield the most
efficient template banks at low dimensions (n < 10), while random template
banks increasingly outperform any other method at higher dimensions.Comment: 13 pages, 10 figures, submitted to PR
Phase diagram of QCD with two degenerate staggered quarks
We present preliminary results about the critical line of QCD with two
degenerate staggered quarks at nonzero temperature and chemical potential,
obtained by the method of analytic continuation. As in our previous studies
with different numbers of colors and flavors, we find deviations from a simple
quadratic dependence on the chemical potential. We comment on the shape of the
critical line at real chemical potential and give an estimate of the curvature
of the critical line, both for quark chemical potential and isospin chemical
potential.Comment: 7 pages, 6 figures, talk presented at Lattice 2011, The XXIX
International Symposium on Lattice Field Theory, Squaw Valley, Lake Tahoe,
California, USA, July 11-16, 201
- …