1,824 research outputs found
A geometric method for model reduction of biochemical networks with polynomial rate functions
The Gravitational Sector in the Connes-Lott Formulation of the Standard Model
We study the Riemannian aspect and the Hilbert-Einstein gravitational action
of the non-commutative geometry underlying the Connes-Lott construction of the
action functional of the standard model. This geometry involves a two-sheeted,
Euclidian space-time. We show that if we require the space of forms to be
locally isotropic and the Higgs scalar to be dynamical, then the Riemannian
metrics on the two sheets of Euclidian space-time must be identical. We also
show that the distance function between the two sheets is determined by a
single, real scalar field whose VEV sets the weak scale.Comment: Latex file, 29 page
Adaiabtic theorems and reversible isothermal processes
Isothermal processes of a finitely extended, driven quantum system in contact
with an infinite heat bath are studied from the point of view of quantum
statistical mechanics. Notions like heat flux, work and entropy are defined for
trajectories of states close to, but distinct from states of joint thermal
equilibrium. A theorem characterizing reversible isothermal processes as
quasi-static processes (''isothermal theorem'') is described. Corollaries
concerning the changes of entropy and free energy in reversible isothermal
processes and on the 0th law of thermodynamics are outlined
Laminar and turbulent dynamos in chiral magnetohydrodynamics-I: Theory
The magnetohydrodynamic (MHD) description of plasmas with relativistic
particles necessarily includes an additional new field, the chiral chemical
potential associated with the axial charge (i.e., the number difference between
right- and left-handed relativistic fermions). This chiral chemical potential
gives rise to a contribution to the electric current density of the plasma
(\emph{chiral magnetic effect}). We present a self-consistent treatment of the
\emph{chiral MHD equations}, which include the back-reaction of the magnetic
field on a chiral chemical potential and its interaction with the plasma
velocity field. A number of novel phenomena are exhibited. First, we show that
the chiral magnetic effect decreases the frequency of the Alfv\'{e}n wave for
incompressible flows, increases the frequencies of the Alfv\'{e}n wave and of
the fast magnetosonic wave for compressible flows, and decreases the frequency
of the slow magnetosonic wave. Second, we show that, in addition to the
well-known laminar chiral dynamo effect, which is not related to fluid motions,
there is a dynamo caused by the joint action of velocity shear and chiral
magnetic effect. In the presence of turbulence with vanishing mean kinetic
helicity, the derived mean-field chiral MHD equations describe turbulent
large-scale dynamos caused by the chiral alpha effect, which is dominant for
large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an
interaction of the chiral magnetic effect and fluctuations of the small-scale
current produced by tangling magnetic fluctuations (which are generated by
tangling of the large-scale magnetic field by sheared velocity fluctuations).
These dynamo effects may have interesting consequences in the dynamics of the
early universe, neutron stars, and the quark--gluon plasma.Comment: 23 pages, 4 figure
A model with simultaneous first and second order phase transitions
We introduce a two dimensional nonlinear XY model with a second order phase
transition driven by spin waves, together with a first order phase transition
in the bond variables between two bond ordered phases, one with local
ferromagnetic order and another with local antiferromagnetic order. We also
prove that at the transition temperature the bond-ordered phases coexist with a
disordered phase as predicted by Domany, Schick and Swendsen. This last result
generalizes the result of Shlosman and van Enter (cond-mat/0205455). We argue
that these phenomena are quite general and should occur for a large class of
potentials.Comment: 7 pages, 7 figures using pstricks and pst-coi
On the Mean-Field Limit of Bosons with Coulomb Two-Body Interaction
In the mean-field limit the dynamics of a quantum Bose gas is described by a
Hartree equation. We present a simple method for proving the convergence of the
microscopic quantum dynamics to the Hartree dynamics when the number of
particles becomes large and the strength of the two-body potential tends to 0
like the inverse of the particle number. Our method is applicable for a class
of singular interaction potentials including the Coulomb potential. We prove
and state our main result for the Heisenberg-picture dynamics of "observables",
thus avoiding the use of coherent states. Our formulation shows that the
mean-field limit is a "semi-classical" limit.Comment: Corrected typos and included an elementary proof of the Kato
smoothing estimate (Lemma 6.1
Eine mechanisierte kompetitive Proteinbindungsanalyse für Cortisol im Serum ohne vorherige Extraktion mit organischen Lösungsmitteln
Peer Reviewe
- …