13,787 research outputs found
Mean field baryon magnetic moments and sumrules
New developments have spurred interest in magnetic moments (-s) of
baryons. The measurement of some of the decuplet -s and the findings of
new sumrules from various methods are partly responsible for this renewed
interest. Our model, inspired by large colour approximation, is a relativistic
self consistent mean field description with a modified Richardson potential and
is used to describe the -s and masses of all baryons with up (u), down (d)
and strange (s) quarks. We have also checked the validity of the Franklin
sumrule (referred to as CGSR in the literature) and sumrules of Luty,
March-Russell and White. We found that our result for sumrules matches better
with experiment than the non-relativistic quark model prediction. We have also
seen that quark magnetic moments depend on the baryon in which they belong
while the naive quark model expects them to be constant.Comment: 7 pages, no figure, uses epl.cl
Keck Observations of the Most Distant Galaxy: 8C1435+63 at z=4.25
We report on Keck observations and confirm the redshift of the most distant
galaxy known: 8C1435+63 at z=4.25. The spectrum shows a strong Ly line,
a Ly forest continuum break and a continuum break at
\AA. The Ly emission is spatially extended and
roughly aligned with the radio source. The galaxy shows a double structure in
the -band (1500\AA) which is aligned with the radio
axis; the two -band components spatially coincide with the nuclear and
southern radio components. Some fraction of the band emission could be due
to a nonthermal process such as inverse compton scattering. In the -band
(4200\AA), which may be dominated by starlight, the
galaxy has a very low surface brightness, diffuse morphology. The
morphology shows little relationship to the radio source structure, although
the major axis of the emission is elongated roughly in the direction of the
radio source axis. The galaxian continuum is very red () and if the
continuum is due to starlight, implies a formation redshift of . We
speculate that this galaxy may be the progenitor of a present day cD galaxy.Comment: 4 pages + 4 figures; uuencoded tar compressed PostScript files;
figures and tables included. To appear in 1 Jan 1995 issue of The
Astrophysical Journal, Letters. Please direct requests/questions/comments to
[email protected]
Maximum mass of a cold compact star
We calculate the maximum mass of the class of compact stars described by
Vaidya-Tikekar \cite{VT01} model. The model permits a simple method of
systematically fixing bounds on the maximum possible mass of cold compact stars
with a given value of radius or central density or surface density. The
relevant equations of state are also determined. Although simple, the model is
capable of describing the general features of the recently observed very
compact stars. For the calculation, no prior knowledge of the equation of state
(EOS) is required. This is in contrast to the earlier calculations for maximum
mass which were done by choosing first the relevant EOSs and using those to
solve the TOV equation with appropriate boundary conditions. The bounds
obtained by us are comparable and, in some cases, more restrictive than the
earlier results.Comment: 18 pages including 4 *.eps figures. Submitted for publicatio
Behaviour of the EAS Age Parameter in the Knee Energy Region
Analyzing simulated EAS events generated with the CORSIKA code, the
characteristics of lateral distribution of electrons in EAS around the knee
energy region of the primary energy spectrum have been studied and compared
with experimental observations. The differences between the EGS4 and the NKG
output of CORSIKA in respect to electron radial density distribution have been
investigated. The relation between lateral and longitudinal age parameters has
been studied after introducing the notion of the local age parameter that
reflects the profile of the lateral distribution of electrons in EAS. The
present analysis motivates the inclusion of the lateral shower age in a
multiparameter study of EAS to extract information on hadronic interactions and
primary composition.Comment: Talk presented at XVI International Symposium on Very High Energy
Cosmic Ray Interactions (ISVHECRI 2010), Batavia, IL, USA (28 June - 2 July
2010). 4 pages, 5 figure
Spatial Structures and Giant Number Fluctuations in Models of Active Matter
The large scale fluctuations of the ordered state in active matter systems
are usually characterised by studying the "giant number fluctuations" of
particles in any finite volume, as compared to the expectations from the
central limit theorem. However, in ordering systems, the fluctuations in
density ordering are often captured through their structure functions deviating
from Porod law. In this paper we study the relationship between giant number
fluctuations and structure functions, for different models of active matter as
well as other non-equilibrium systems. A unified picture emerges, with
different models falling in four distinct classes depending on the nature of
their structure functions. For one class, we show that experimentalists may
find Porod law violation, by measuring subleading corrections to the number
fluctuations.Comment: 5 pages, 3 figure
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