292 research outputs found
An Expanding Shell of Neutral Hydrogen Associated with SN 1006: Hints for the Single-Degenerate Origin and Faint Hadronic Gamma-Rays
We report new HI observations of the Type Ia supernova remnant SN 1006 using
the Australia Telescope Compact Array with an angular resolution of (2 pc at the assumed SNR distance of 2.2 kpc). We find an
expanding gas motion in position-velocity diagrams of HI with an expansion
velocity of 4 km s and a mass of 1000 . The spatial
extent of the expanding shell is roughly the same as that of SN 1006. We here
propose a hypothesis that SN 1006 exploded inside the wind-blown bubble formed
by accretion winds from the progenitor system consisting of a white dwarf and a
companion star, and then the forward shock has already reached the wind wall.
This scenario is consistent with the single-degenerate model. We also derived
the total energy of cosmic-ray protons to be only 1.2- erg by adopting the averaged interstellar proton density of
25 cm. The small value is compatible with the relation between the
age and of other gamma-ray supernova remnants with ages below
6 kyr. The value in SN 1006 will possibly increase up to
several 10 erg in the next 5 kyr via the cosmic-ray diffusion into
the HI wind-shell.Comment: 12 pages, 4 figures, 1 table, accepted for publication in The
Astrophysical Journal (ApJ
Isothermal remanent magnetization and the spin dimensionality of spin glasses
The isothermal remanent magnetization is used to investigate dynamical
magnetic properties of spatially three dimensional spin glasses with different
spin dimensionality (Ising, XY, Heisenberg). The isothermal remanent
magnetization is recorded vs. temperature after intermittent application of a
weak magnetic field at a constant temperature . We observe that in the
case of the Heisenberg spin glasses, the equilibrated spin structure and the
direction of the excess moment are recovered at . The isothermal remanent
magnetization thus reflects the directional character of the
Dzyaloshinsky-Moriya interaction present in Heisenberg systems.Comment: tPHL2e style; 7 page, 3 figure
Spin Glasses: Model systems for non-equilibrium dynamics
Spin glasses are frustrated magnetic systems due to a random distribution of
ferro- and antiferromagnetic interactions. An experimental three dimensional
(3d) spin glass exhibits a second order phase transition to a low temperature
spin glass phase regardless of the spin dimensionality. In addition, the low
temperature phase of Ising and Heisenberg spin glasses exhibits similar
non-equilibrium dynamics and an infinitely slow approach towards a
thermodynamic equilibrium state. There are however significant differences in
the detailed character of the dynamics as to memory and rejuvenation phenomena
and the influence of critical dynamics on the behaviour. In this article, some
aspects of the non-equilibrium dynamics of an Ising and a Heisenberg spin glass
are briefly reviewed and some comparisons are made to other glassy systems that
exhibit magnetic non-equilibrium dynamics.Comment: To appear in J. Phys.: Condens. Matter, Proceedings from HFM2003,
Grenobl
"Glassy Dynamics" in Ising Spin Glasses -- Experiment and Simulation
The field-cooled magnetization (FCM) processes of Ising spin glasses under
relatively small fields are investigated by experiment on
Fe_{0.55}Mn_{0.45}TiO_3 and by numerical simulation on the three-dimensional
Edwards-Anderson model. Both results are explained in a unified manner by means
of the droplet picture. In particular, the cusp-like behavior of the FCM is
interpreted as evidence, not for an equilibrium phase transition under a finite
magnetic field, but for a dynamical (`blocking') transition frequently observed
in glassy systems.Comment: 4 pages, 7 figure
Expression pattern of annelid Zic in embryonic development of the oligochaete Tubifex tubifex
Aging, rejuvenation and memory effects in Ising and Heisenberg spin glasses
We have compared aging phenomena in the Fe_{0.5}Mn_{0.5}TiO_3 Ising spin
glass and in the CdCr_{1.7}In_{0.3}S_4 Heisenberg-like spin glass by means of
low-frequency ac susceptibility measurements. At constant temperature, aging
obeys the same ` scaling' in both samples as in other systems.
Investigating the effect of temperature variations, we find that the Ising
sample exhibits rejuvenation and memory effects which are qualitatively similar
to those found in other spin glasses, indicating that the existence of these
phenomena does not depend on the dimensionality of the spins. However,
systematic temperature cycling experiments on both samples show important
quantitative differences. In the Ising sample, the contribution of aging at low
temperature to aging at a slightly higher temperature is much larger than
expected from thermal slowing down. This is at variance with the behaviour
observed until now in other spin glasses, which show the opposite trend of a
free-energy barrier growth as the temperature is decreased. We discuss these
results in terms of a strongly renormalized microscopic attempt time for
thermal activation, and estimate the corresponding values of the barrier
exponent introduced in the scaling theories.Comment: 8 pages, including 6 figure
Time and length scales in spin glasses
We discuss the slow, nonequilibrium, dynamics of spin glasses in their glassy
phase. We briefly review the present theoretical understanding of the
spectacular phenomena observed in experiments and describe new numerical
results obtained in the first large-scale simulation of the nonequilibrium
dynamics of the three dimensional Heisenberg spin glass.Comment: Paper presented at "Highly Frustrated Magnetism 2003", Grenoble,
August 200
Neutron scattering study of transverse magnetism
In order to clarify the nature of the additional phase transition at H1 (T) \u3c Hc (T) of the layered antiferromagnetic (AF) insulator FeBr2 as found by Aruga Katori et al. (1996) we measured the intensity of different Bragg-peaks in different scattering geometries. Transverse AF ordering is observed in both AF phases, AFI and AFII. Its order parameter exhibits a peak at T1 = T (H1) in temperature scans and does not vanish in zero field. Possible origins of the step-like increase of the transverse ferromagnetic ordering induced by a weak in-plane field component when entering AFI below T1 are discussed
Aging, rejuvenation and memory phenomena in spin glasses
In this paper, we review several important features of the out-of-equilibrium
dynamics of spin glasses. Starting with the simplest experiments, we discuss
the scaling laws used to describe the isothermal aging observed in spin glasses
after a quench down to the low temperature phase. We report in particular new
results on the sub-aging behaviour of spin glasses. We then discuss the
rejuvenation and memory effects observed when a spin glass is submitted to
temperature variations during aging, from the point of view of both energy
landscape pictures and of real space pictures. We highlight the fact that both
approaches point out the necessity of hierarchical processes involved in aging.
Finally, we report an investigation of the effect of small temperature
variations on aging in spin glass samples with various anisotropies which
indicates that this hierarchy depends on the spin anisotropy.Comment: submitted for the Proceedings of Stat Phys 22, Bangalore (India
Field-Shift Aging Protocol on the 3D Ising Spin-Glass Model: Dynamical Crossover between the Spin-Glass and Paramagnetic States
Spin-glass (SG) states of the 3-dimensional Ising Edwards-Anderson model
under a static magnetic field are examined by means of the standard Monte
Carlo simulation on the field-shift aging protocol at temperature . For each
process with (T; \tw, h), \tw being the waiting time before the field is
switched on, we extract the dynamical crossover time, \tcr(T; \tw, h). We
have found a nice scaling relation between the two characteristic length scales
which are properly determined from \tcr and \tw and then are normalized by
the static field crossover length introduced in the SG droplet theory. This
scaling behavior implies the instability of the SG phase in the equilibrium
limit even under an infinitesimal . In comparison with this numerical result
the field effect on real spin glasses is also discussed.Comment: 4 pages, 5 figures, jpsj2, Changed conten
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