1,674 research outputs found
Abelian monopoles and center vortices in Yang-Mills plasma
Condensation of the Abelian monopoles and the center vortices leads to
confinement of color in low temperature phase of Yang-Mills theory. We stress
that these topological magnetic degrees of freedom are also very important in
the deconfinement regime: at the point of the deconfinement phase transition
both the monopoles and the vortices are released into the thermal vacuum
contributing, in particular, to the equation of state and, definitely, to
transport properties of the hot gluonic medium. Thus, we argue that a novel,
magnetic component plays a crucial role. On the other hand, it was demonstrated
that an effective three-dimensional description can be brought, beginning with
high temperatures, down to the critical temperature by postulating existence of
a system of 3d Higgs fields. We propose to identify the 3d color-singlet Higgs
field with the 3d projection of the 4d magnetic vortices. Such identification
fits well the 3d properties of the theory and contributes to interpretation of
the magnetic component of the Yang-Mills plasma.Comment: 5 pages, 3 figures; talk at Quark Confinement and the Hadron
Spectrum, September 1-6 2008, Mainz, German
RGS4 regulates partial agonism of the M2 muscarinic receptor-activated K+ currents.
Partial agonists are used clinically to avoid overstimulation of receptor-mediated signalling, as they produce a submaximal response even at 100% receptor occupancy. The submaximal efficacy of partial agonists is due to conformational change of the agonist-receptor complex, which reduces effector activation. In addition to signalling activators, several regulators help control intracellular signal transductions. However, it remains unclear whether these signalling regulators contribute to partial agonism. Here we show that regulator of G-protein signalling (RGS) 4 is a determinant for partial agonism of the M2 muscarinic receptor (M2R). In rat atrial myocytes, pilocarpine evoked smaller G-protein-gated K(+) inwardly rectifying (KG) currents than those evoked by ACh. In a Xenopus oocyte expression system, pilocarpine acted as a partial agonist in the presence of RGS4 as it did in atrial myocytes, while it acted like a full agonist in the absence of RGS4. Functional couplings within the agonist-receptor complex/G-protein/RGS4 system controlled the efficacy of pilocarpine relative to ACh. The pilocarpine-M2R complex suppressed G-protein-mediated activation of KG currents via RGS4. Our results demonstrate that partial agonism of M2R is regulated by the RGS4-mediated inhibition of G-protein signalling. This finding helps us to understand the molecular components and mechanism underlying the partial agonism of M2R-mediated physiological responses
Nonlinear Pattern Selection in Binary Mixture Convection with Through-Flow
The pattern selection problem in binary-mixture convection in an extended
channel with a lateral through-flow is presented. The through-flow breaks
left--right parity and changes pattern dynamics dramatically. The problem is
studied based on computer simulation of the complete set of hydrodynamic
equations (Oberbeck-Boussinesq approximation) in the two-dimensional
rectangular channel with aspect ratio and convection-suppressing
lateral boundary conditions. A wide variety of new dynamical patterns is
obtained, discussed and classified.Comment: 9 pages and 2 figure
Gluon propagators and center vortices at finite temperature
We study influence of center vortices on infrared properties of gluons in the
deconfinement phase of quenched QCD. We observe a significant suppression of
the magnetic component of the gluon propagator in the low-momentum region after
the vortices are removed from the gluon configurations. The propagator of the
electric gluon stays almost unaffected by the vortex removal. Our results
demonstrate that the center vortices are responsible for important
nonperturbative properties of the magnetic component of the quark-gluon plasma.Comment: 7 pages, 8 figures, talk presented at 27th International Symposium on
Lattice Field Theory (Lattice 2009), Beijing, 26-31 Jul 200
Laser pulse-shape dependence of Compton scattering
Compton scattering of short and ultra short (sub-cycle) laser pulses off
mildly relativistic electrons is considered within a QED framework. The
temporal shape of the pulse is essential for the differential cross section as
a function of the energy of the scattered photon at fixed observation angle.
The partly integrated cross section is sensitive to the non-linear dynamics
resulting in a large enhancement of the cross section for short and, in
particular, for ultra-short flat-top pulse envelopes which can reach several
orders of magnitude, as compared with the case of a long pulse. Such effects
can be studied experimentally and must be taken into account in
Monte-Carlo/transport simulations of % pair production in the
interaction of electrons and photons in a strong laser field.Comment: 14 pages, 12 figure
Determination of the carrier envelope phase for short, circularly polarized laser pulses
We analyze the impact of the carrier envelope phase on the differential cross
sections of the Breit-Wheeler and the generalized Compton scattering in the
interaction of a charged electron (positron) with an intensive ultra-short
electromagnetic (laser) pulse. The differential cross sections as a function of
the azimuthal angle of the outgoing electron have a clear bump structure, where
the bump position coincides with the value of the carrier phase. This effect
can be used for the carrier envelope phase determination.Comment: 7 pages, 4 figure
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