30,922 research outputs found
On the Global Regularity of a Helical-decimated Version of the 3D Navier-Stokes Equations
We study the global regularity, for all time and all initial data in
, of a recently introduced decimated version of the incompressible 3D
Navier-Stokes (dNS) equations. The model is based on a projection of the
dynamical evolution of Navier-Stokes (NS) equations into the subspace where
helicity (the scalar product of velocity and vorticity) is sign-definite.
The presence of a second (beside energy) sign-definite inviscid conserved
quadratic quantity, which is equivalent to the Sobolev norm, allows
us to demonstrate global existence and uniqueness, of space-periodic solutions,
together with continuity with respect to the initial conditions, for this
decimated 3D model. This is achieved thanks to the establishment of two new
estimates, for this 3D model, which show that the and the time
average of the square of the norms of the velocity field remain
finite. Such two additional bounds are known, in the spirit of the work of H.
Fujita and T. Kato \cite{kato1,kato2}, to be sufficient for showing
well-posedness for the 3D NS equations. Furthermore, they are directly linked
to the helicity evolution for the dNS model, and therefore with a clear
physical meaning and consequences
Superfluid Bose-Fermi mixture from weak-coupling to unitarity
We investigate the zero-temperature properties of a superfluid Bose-Fermi
mixture by introducing a set of coupled Galilei-invariant nonlinear
Schr\"odinger equations valid from weak-coupling to unitarity. The Bose
dynamics is described by a Gross-Pitaevskii-type equation including
beyond-mean-field corrections possessing the correct weak-coupling and
unitarity limits. The dynamics of the two-component Fermi superfluid is
described by a density-functional equation including beyond-mean-field terms
with correct weak-coupling and unitarity limits. The present set of equations
is equivalent to the equations of generalized superfluid hydrodynamics, which
take into account also surface effects. The equations describe the mixture
properly as the Bose-Bose repulsive (positive) and Fermi-Fermi attractive
(negative) scattering lengths are varied from zero to infinity in the presence
of a Bose-Fermi interaction. The present model is tested numerically as the
Bose-Bose and Fermi-Fermi scattering lengths are varied over wide ranges
covering the weak-coupling to unitarity transition.Comment: 11 page
Medical use of cannabis: italian and european legislation
This review illustrates some brief
considerations of the medical use of cannabis recently
issued in Italy. History and uses of cannabis
throughout centuries and different countries
are illustrated together with a description of botany
and active phytocannabinoids. Then, medical
use of cannabis anti-pain treatment for patients
resistant to conventional therapies is described
in case of chronic neuropathic pain, spasticity,
for anticinetosic and antiemetic effect in nausea
and vomiting caused by chemotherapy, for appetite
stimulating effect in cachexia, anorexia, loss
of appetite in cancer patients or patients with
AIDS and in anorexia nervosa, hypotensive effect
in glaucoma resistant to conventional therapies
and for reduction of involuntary body and facial
movements in Gilles de la Tourette syndrome.
Italian most recent legislation on medical cannabis
is detailed with some law proposals, also
showing the inconsistent legislation within European
Union. Some final considerations of future
studies are also reported
Aspects of symmetry breaking in SO(10) GUTs
I review some recent results on the Higgs sector of minimal SO(10) grand
unified theories both with and without supersymmetry. It is shown that
nonsupersymmetric SO(10) with just one adjoint triggering the first stage of
the symmetry breaking does provide a successful gauge unification when
radiative corrections are taken into account in the scalar potential, while in
the supersymmetric case it is argued that the troubles in achieving a
phenomenologically viable breaking with representations up to the adjoint are
overcome by considering the flipped SO(10) embedding of the hypercharge.Comment: 8 pages, 1 figure; prepared for the proceedings of DISCRETE'10 -
Symposium on Prospects in the Physics of Discrete Symmetrie
Contributions of cortical feedback to sensory processing in primary visual cortex
Closing the structure-function divide is more challenging in the brain than in any other organ (Lichtman and Denk, 2011). For example, in early visual cortex, feedback projections to V1 can be quantified (e.g., Budd, 1998) but the understanding of feedback function is comparatively rudimentary (Muckli and Petro, 2013). Focusing on the function of feedback, we discuss how textbook descriptions mask the complexity of V1 responses, and how feedback and local activity reflects not only sensory processing but internal brain states
A Parallel Hamiltonian Eigensolver for Passivity Characterization and Enforcement of Large Interconnect Macromodels
Best Paper Award Nominatio
Finite times to equipartition in the thermodynamic limit
We study the time scale T to equipartition in a 1D lattice of N masses
coupled by quartic nonlinear (hard) springs (the Fermi-Pasta-Ulam beta model).
We take the initial energy to be either in a single mode gamma or in a package
of low frequency modes centered at gamma and of width delta-gamma, with both
gamma and delta-gamma proportional to N. These initial conditions both give,
for finite energy densities E/N, a scaling in the thermodynamic limit (large
N), of a finite time to equipartition which is inversely proportional to the
central mode frequency times a power of the energy density E/N. A theory of the
scaling with E/N is presented and compared to the numerical results in the
range 0.03 <= E/N <= 0.8.Comment: Plain TeX, 5 `eps' figures, submitted to Phys. Rev.
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