8 research outputs found
Two dimensional SU(N)xSU(N) Chiral Models on the Lattice (II): the Green's Function
Analytical and numerical methods are applied to principal chiral models on a
two-dimensional lattice and their predictions are tested and compared. New
techniques for the strong coupling expansion of SU(N) models are developed and
applied to the evaluation of the two-point correlation function. The
momentum-space lattice propagator is constructed with precision O(\beta^{10})
and an evaluation of the correlation length is obtained for several different
definitions. Three-loop weak coupling contributions to the internal energy and
to the lattice and functions are evaluated for all N, and the
effect of adopting the ``energy'' definition of temperature is computed with
the same precision. Renormalization-group improved predictions for the
two-point Green's function in the weak coupling ( continuum ) regime are
obtained and successfully compared with Monte Carlo data. We find that strong
coupling is predictive up to a point where asymptotic scaling in the energy
scheme is observed. Continuum physics is insensitive to the effects of the
large N phase transition occurring in the lattice model. Universality in N is
already well established for and the large N physics is well
described by a ``hadronization'' picture.Comment: Revtex, 37 pages, 16 figures available on request by FAX or mai
A numerical code for the simulation of transient multicomponent magma dynamics
A numerical code for the simulation of the dynamics of multicomponent fluids based on the highly stable and accurate finite element algorithm by Hauke and Hughes (1998) has been implemented. This numerical method allows a unified approach forcompressible and incompressible transient flows. Therefore, it is particularly suitable for the simulation of the dynamics within magma chambers and along volcanic conduits,
where a wide range of Mach and Reynolds numbers occurs. The balance equations of mass, momentum, energy, and composition are solved for the unknowns pressure, velocity, temperature, and composition of a homogeneous mixture with properties dependent on the local conditions. The equations are discretized in time and space with Galerkin least-squares and discontinuity-capturing stabilizing techniques.
The conservation equations for chemical components have been added to the original Hauke and Hughes (1998) formulation, along with the corresponding stabilization
terms. The linear non-symmetric system of discretized equations is solved with a preconditioned GMRES. The code is written in C++, picking up FE and mathematical
tools from the open source OFELI, Diffpack, and MTL libraries. The computational results have been validated on classical test cases in a wide range of flow conditions from compressible to incompressible. Applications to magma chamber and conduit flow dynamic problems show several features of the multidimensional transient dynamics before, during, and after volcanic eruptions
Detecting fundamental fields with LISA observations of gravitational waves from extreme mass-ratio inspirals
The Laser Interferometer Space Antenna, LISA, will detect gravitational wave
signals from Extreme Mass Ratio Inspirals, where a stellar mass compact object
orbits a supermassive black hole and eventually plunges into it. Here we report
on LISA's capability to detect whether the smaller compact object in an Extreme
Mass Ratio Inspiral is endowed with a scalar field, and to measure its scalar
charge -- a dimensionless quantity that acts as a measure of how much scalar
field the object carries. By direct comparison of signals, we show that LISA
will be able to detect and measure the scalar charge with an accuracy of the
order of percent, which is an unprecedented level of precision. This result is
independent of the origin of the scalar field and of the structure and other
properties of the small compact object, so it can be seen as a generic
assessment of LISA's capabilities to detect new fundamental fields.Comment: Typo corrected to match the version in pres
Evolution of genes and genomes on the Drosophila phylogeny
Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species
Evolution of genes and genomes on the Drosophila phylogeny
Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species
Evolution of genes and genomes on the Drosophila phylogeny
Affiliations des auteurs : cf page 216 de l'articleInternational audienceComparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species