7 research outputs found
Symmetries of microcanonical entropy surfaces
Symmetry properties of the microcanonical entropy surface as a function of
the energy and the order parameter are deduced from the invariance group of the
Hamiltonian of the physical system. The consequences of these symmetries for
the microcanonical order parameter in the high energy and in the low energy
phases are investigated. In particular the breaking of the symmetry of the
microcanonical entropy in the low energy regime is considered. The general
statements are corroborated by investigations of various examples of classical
spin systems.Comment: 15 pages, 5 figures include
Pulsar shadow as the origin of double notches in radio pulse profiles
We present the model of eclipsing a rotating, spatially extended source of
directional emission by a central absorber, and apply it to the pulsar
magnetosphere. The model assumes the radially extended inward radio emission
along the local direction of the magnetic field, and the pulsar as the
absorber. The geometry of the magnetic field lines of the rotating dipole is
favourable for the double eclipse events, which we identify with the double
notches observed in pulse profiles of nearby pulsars. For pulsars with large
dipole inclinations 70 <~ alpha <~ 110 deg the double notches are predicted to
occur within a narrow phase range of 20 to 30 deg before the main radio peak.
Application of the model to PSR B0950+08 establishes it as a nearly orthogonal
rotator (alpha =~ 75 deg, beta =~ -10 deg) with many pulse components naturally
interpreted in terms of the inward radio emission from a large range of
altitudes. The inward components include the intermittently strong, leading
component of the main pulse, which would traditionally have been interpeted as
a conal emission in the outward direction. The model also identifies the
magnetic field lines along which the radially extended inward radio emission
occurs in B0950+08. These have a narrow range of the footprint parameter s
close to 1.1 (closed field line region, near the last open field lines). We
describe directional characteristics of inward emission from the radially
extended region and compare them with characteristics of extended outward
emission. Our work shows that pulse profiles of at least some pulsars may be a
superposition of both inward and outward emission.Comment: 28 pages, 13 figures, accepted by ApJ, high-quality figures are
available from http://www.ncac.torun.pl/~michalf/inward1_figs