155 research outputs found
Strangeness in Neutron Stars
It is generally agreed on that the tremendous densities reached in the
centers of neutron stars provide a high-pressure environment in which numerous
novel particles processes are likely to compete with each other. These
processes range from the generation of hyperons to quark deconfinement to the
formation of kaon condensates and H-matter. There are theoretical suggestions
of even more exotic processes inside neutron stars, such as the formation of
absolutely stable strange quark matter, a configuration of matter even more
stable than the most stable atomic nucleus, iron. In the latter event, neutron
stars would be largely composed of pure quark matter, eventually enveloped in a
thin nuclear crust. No matter which physical processes are actually realized
inside neutron stars, each one leads to fingerprints, some more pronounced than
others though, in the observable stellar quantities. This feature combined with
the unprecedented progress in observational astronomy, which allows us to see
vistas with remarkable clarity that previously were only imagined, renders
neutron stars to nearly ideal probes for a wide range of physical studies,
including the role of strangeness in dense matter.Comment: 15 pages, 6 figures, Presented at the 5th International Conference on
Strangeness in Quark Matter (Strangeness 2000), Berkeley, California, USA,
July 20-25, 200
Are strange stars distinguishable from neutron stars by their cooling behaviour?
The general statement that strange stars cool more rapidly than neutron stars
is investigated in greater detail. It is found that the direct Urca process
could be forbidden not only in neutron stars but also in strange stars. If so,
strange stars would be slowly cooling and their surface temperatures would be
more or less indistinguishable from those of slowly cooling neutron stars. The
case of enhanced cooling is reinvestigated as well. It is found that strange
stars cool significantly more rapidly than neutron stars within the first years after birth. This feature could become particularly interesting if
continued observation of SN 1987A would reveal the temperature of the possibly
existing pulsar at its centre.Comment: 10 pages, 3 ps-figures, to appear in the proceedings of the
International Symposium on ''Strangeness in Quark Matter 1997``, April
14--18, Thera (Santorini), Hella
The Principle of Non-Gravitating Vacuum Energy and some of its consequences
For Einstein's General Relativity (GR) or the alternatives suggested up to
date the vacuum energy gravitates. We present a model where a new measure is
introduced for integration of the total action in the D-dimensional space-time.
This measure is built from D scalar fields . As a consequence of
such a choice of the measure, the matter lagrangian can be changed by
adding a constant while no gravitational effects, like a cosmological term, are
induced. Such Non-Gravitating Vacuum Energy (NGVE) theory has an infinite
dimensional symmetry group which contains volume-preserving diffeomorphisms in
the internal space of scalar fields . Other symmetries contained
in this symmetry group, suggest a deep connection of this theory with theories
of extended objects. In general {\em the theory is different from GR} although
for certain choices of , which are related to the existence of an
additional symmetry, solutions of GR are solutions of the model. This is
achieved in four dimensions if is due to fundamental bosonic and
fermionic strings. Other types of matter where this feature of the theory is
realized, are for example: scalars without potential or subjected to nonlinear
constraints, massless fermions and point particles. The point particle plays a
special role, since it is a good phenomenological description of matter at
large distances. de Sitter space is realized in an unconventional way, where
the de Sitter metric holds, but such de Sitter space is supported by the
existence of a variable scalar field which in practice destroys the maximal
symmetry. The only space - time where maximal symmetry is not broken, in a
dynamical sense, is Minkowski space. The theory has non trivial dynamics in 1+1
dimensions, unlike GR.Comment: 23 page
New Physics Potential with a Neutrino Telescope
Active Galactic Nuclei are considered as sources of neutrinos, with neutrino
energies extending up to 10^{18} eV. It is expected that these highly energetic
cosmic neutrinos will be detected by the neutrino telescopes, presently under
construction. The detection process is very sensitive to the total muon
neutrino cross-section. We examine how the total cross section changes at high
energies, by the single production of excited fermions (excited muon and
muon-neutrino). For parameters (masses, couplings) of the excited fermions
allowed by the experimental constraints, we find that for energies of the
incoming muon-neutrino above 100 TeV the cross-section for single production of
(excited muon and muon-neutrino) supersedes the standard total cross-section.Comment: 12 pages and 2 figures; typset using revtex; postscript files for the
figures provide
Naturalness Bounds on Dipole Moments from New Physics
Assuming naturalness that the quantum corrections to the mass should not
exceed the order of the observed mass, we derive and apply model-independent
bounds on the anomalous magnetic moments and electric dipole moments of leptons
and quarks due to new physics.Comment: 4 pages, 2 figure
Strange Star Heating Events as a Model for Giant Flares of Soft Gamma-ray Repeaters
Two giant flares were observed on 5 March 1979 and 27 August 1998 from the
soft gamma-ray repeaters SGR 0526-66 and SGR 1900+14, respectively. The
striking similarity between these remarkable bursts strongly implies a common
nature. We show that the light curves of the giant bursts may be easily
explained in the model where the burst radiation is produced by the bare quark
surface of a strange star heated, for example, by impact of a massive
comet-like object.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. Letter
Long range neutrino forces in the cosmic relic neutrino background
Neutrinos mediate long range forces among macroscopic bodies in vacuum. When
the bodies are placed in the neutrino cosmic background, these forces are
modified. Indeed, at distances long compared to the scale , the relic
neutrinos completely screen off the 2-neutrino exchange force, whereas for
small distances the interaction remains unaffected.Comment: 8 pages, 2 figure
Discriminating New Physics Scenarios at NLC: The Role of Polarization
We explore the potential of the Next Linear Collider (NLC), operating in the
mode, to disentangle new physics scenarios on single production.
We study the effects related with the exchange of composite fermion in the
reaction , and compare with those arising from trilinear
gauge boson anomalous couplings. We stress the role played by the initial state
polarization to increase the reach of this machine and to discriminate the
possible origin of the new phenomena.Comment: 26 pages, LaTeX file using ReVTeX. 10 Figure
Production in Two-Photon Processes at TRISTAN
We have carried out an inclusive measurement of production
in two-photon processes at TRISTAN. The mean was 58 GeV and the
integrated luminosity was 199 pb. High-statistics samples were
obtained under such conditions as no-, anti-electron, and remnant-jet tags. The
remnant-jet tag, in particular, allowed us, for the first time, to measure the
cross sections separately for the resolved-photon and direct processes.Comment: 20 pages, Latex format, 4 figures and KEK-mark included. Table 1
revised. To be published in Phys. Lett.
Model of the Quark Mixing Matrix
The structure of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is analyzed from
the standpoint of a composite model. A model is constructed with three families
of quarks, by taking tensor products of sufficient numbers of spin-1/2
representations and imagining the dominant terms in the mass matrix to arise
from spin-spin interactions. Generic results then obtained include the familiar
relation , and a less frequently
seen relation . The magnitudes of
and come out naturally to be of the right order. The phase in
the CKM matrix can be put in by hand, but its origin remains obscure.Comment: Presented by Mihir P. Worah at DPF 92 Meeting, Fermilab, November,
1992. 3 pages, LaTeX fil
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