218 research outputs found
A Spallation Model for the Titanium-rich Supernova Remnant Cassiopeia A
Titanium-rich subluminous supernovae are rare and challenge current SN
nucleosynthesis models. We present a model in which ejecta from a standard
Supernova is impacted by a second explosion of the neutron star (a Quark-nova),
resulting in spallation reactions that lead to 56Ni destruction and 44Ti
creation under the right conditions. Basic calculations of the spallation
products shows that a delay between the two explosions of ~ 5 days reproduces
the observed abundance of 44Ti in Cas A and explains its low luminosity as a
result of the destruction of 56Ni. Our results could have important
implications for lightcurves of subluminous as well as superluminous
supernovae.Comment: Accepted/to be published in Physical Review Letters. [ for more info
on the Quark Nova, see: http://quarknova.ucalgary.ca/
Surface structure of Quark stars with magnetic fields
We investigate the impact of magnetic fields on the electron distribution in
the electrosphere of quark stars. For moderately strong magnetic fields G, quantization effects are generally weak due to the large number
density of electrons at surface, but can nevertheless affect the spectral
features of quark stars. We outline the main observational characteristics of
quark stars as determined by their surface emission, and briefly discuss their
formation in explosive events termed Quark-Novae, which may be connected to the
-process.Comment: 9 pages, 3 figures. Contribution to the proceedings of the IXth
Workshop on High Energy Physics Phenomenology (WHEPP-9), Bhubaneswar, India,
3-14 Jan. 200
Neutrality of a magnetized two-flavor quark superconductor
We investigate the effect of electric and color charge neutrality on the
two-flavor color superconducting (2SC) phase of cold and dense quark matter in
presence of constant external magnetic fields and at moderate baryon densities.
Within the framework of the Nambu-Jona-Lasinio (NJL) model, we study the
inter-dependent evolution of the quark's BCS gap and constituent mass with
increasing density and magnetic field. While confirming previous results
derived for the highly magnetized 2SC phase with color neutrality alone, we
obtain new results as a consequence of imposing charge neutrality. In the
charge neutral gapless 2SC phase (g2SC), a large magnetic field drives the
color superconducting phase transition to a crossover, while the chiral phase
transition is first order. At larger diquark-to-scalar coupling ratio
, where the 2SC phase is preferred, we see hints of the
Clogston-Chandrasekhar limit at a very large value of the magnetic field
(G), but this limit is strongly affected by Shubnikov de
Haas-van Alphen oscillations of the gap, indicating the transition to a
domain-like state.Comment: 19 pages, 7 figures, Matches with the published versio
Magnetar oscillations pose challenges for strange stars
Compact relativistic stars allow us to study the nature of matter under
extreme conditions, probing regions of parameter space that are otherwise
inaccessible. Nuclear theory in this regime is not well constrained: one key
issue is whether neutron stars are in fact composed primarily of strange quark
matter. Distinguishing the two possibilities, however, has been difficult. The
recent detection of seismic vibrations in the aftermath of giant flares from
two magnetars (highly magnetized compact stars) is a major breakthrough. The
oscillations excited seem likely to involve the stellar crust, the properties
of which differ dramatically for strange stars. We show that the resulting mode
frequencies cannot be reconciled with the observations for reasonable magnetar
parameters. Ruling out strange star models would place a strong constraint on
models of dense quark matter.Comment: Parameter space expanded, 5 pages, 3 figures, MNRAS Letters in pres
Quark deconfinement in neutron star cores: The effects of spin-down
We study the role of spin-down in driving quark deconfinement in the high
density core of isolated neutron stars. Assuming spin-down to be solely due to
magnetic braking, we obtain typical timescales to quark deconfinement for
neutron stars that are born with Keplerian frequencies. Employing different
equations of state (EOS), we determine the minimum and maximum neutron star
masses that will allow for deconfinement via spin-down only. We find that the
time to reach deconfinement is strongly dependent on the magnetic field and
that this time is least for EOS that support the largest minimum mass at zero
spin, unless rotational effects on stellar structure are large. For a fiducial
critical density of for the transition to the quark phase
(g/cm is the saturation density of nuclear
matter), we find that neutron stars lighter than cannot reach a
deconfined phase. Depending on the EOS, neutron stars of more than
can enter a quark phase only if they are spinning faster than
about 3 milliseconds as observed now, whereas larger spin periods imply that
they are either already quark stars or will never become one.Comment: 4 pages, 4 figures, submitted to ApJ
Muon production in low-energy electron-nucleon and electron-nucleus scattering
Recently, muon production in electron-proton scattering has been suggested as
a possible candidate reaction for the identification of lepton-flavor violation
due to physics beyond the Standard Model. Here we point out that the
Standard-Model processes and can cloud potential beyond-the-Standard-Model signals in
electron-proton collisions. We find that Standard-Model cross
sections exceed those from lepton-flavor-violating operators by several orders
of magnitude. We also discuss the possibility of using a nuclear target to
enhance the signal.Comment: 24 pages. Additional figure showing energy-dependence of total cross
section, minor changes to text. Conclusions unaltered. This version to appear
in Physical Review
Caprellids (Crustacea: Amphipoda) from India
The caprellid fauna of India is investigated. A
total of 538 samples (including algae, seagrasses, sponges,
hydroids, ascidians, bryozoans, encrusted dead corals, coral
rubble, fine and coarse sediments) were collected from 39
stations along the coast of India, covering a wide diversity
of habitats from intertidal to 12 m water depth. A new
species (Jigurru longimanus n.sp.) is described, and figures
of the 11 valid species reported so far from India are given
together with a key for their identification. No caprellids
were found in sediments from the northeast (16–208N)
coast of India while they were abundant in the southeast
and west coast. Decreases in salinity due to river discharges
associated with lower values of oxygen, higher water
temperatures and lower nutrient inputs along the east coast
could explain these differences in caprellid composition
between the two coastlines. Significantly, lower abundance
of caprellids in India, as in other tropical ecosystems, is
probably related to the lack of species belonging to the
genus Caprella, which reach very high abundances in
temperate waters.Ministerio de Educación y Ciencia de España y fondos FEDER de la Unión Europea. CGL2007-60044/ BOSConsejería de Innovación, Ciencia y Empresa, Junta de Andalucía, España. P07-RNM-02524Ministry of Earth Sciences (MoES) de India. DOD/10-MLR/1/2002/DT 19.12.200
Bremsstrahlung neutrinos from electron-electron scattering in a relativistic degenerate electron plasma
We present a calculation of neutrino pair bremsstrahlung due to
electron-electron scattering in a relativistic degenerate plasma of electrons.
Proper treatment of the in-medium photon propagator, i.e., inclusion of Debye
screening of the longitudinal part and Landau damping of the transverse part,
leads to a neutrino emissivity which is several orders of magnitude larger than
when Debye screening is imposed for the tranverse part. Our results show that
this in-medium process can compete with other sources of neutrino radiation and
can, in some cases, even be the dominant neutrino emission mechanism. We also
discuss the natural extension to quark-quark bremsstrahlung in gapped and
ungapped quark matter.Comment: 15 pages, 7 figure
IN SILICO DOCKING ANALYSIS OF BIOACTIVE COMPOUNDS FROM CALOPHYLLUM INOPHYLLUM L. ETHANOL LEAF EXTRACT AGAINST EGFR PROTEIN
Objective: The objective of this study was to evaluate the effective new phytocomponents from Calophyllum inophyllum ethanol leaf extract against breast cancer target protein of Epidermal Growth Factor Receptor (EGFR) using in silico docking studies.Materials and Methods: The identification of compounds was done by GC-MS analysis. The in silico docking studies were carried out using Discovery Studio 4.0 software.Results: The GC-MS analysis of ethanol leaf extract revealed the presence of eleven compounds. The docking analysis have exhibited moderate to potent inhibition with a range of dock score 3 to 55. 2H-Benzo(cd) pyrene-2,6(1,H)-dione, 3,5,7,10-tetrahydroxy-compound showed the dock score of 55.427.Conclusion: The results revealed out that the compounds present in Calophyllum inophyllum can inhibit the EGFR protein. The plant possesses anticancer potential because of the various bioactive compounds presence which is mainly responsible for anticancer activity.Â
Neutrino Emission from Goldstone Modes in Dense Quark Matter
We calculate neutrino emissivities from the decay and scattering of Goldstone
bosons in the color-flavor-locked (CFL) phase of quarks at high baryon density.
Interactions in the CFL phase are described by an effective low-energy theory.
For temperatures in the tens of keV range, relevant to the long-term cooling of
neutron stars, the emissivities involving Goldstone bosons dominate over those
involving quarks, because gaps in the CFL phase are MeV while the
masses of Goldstone modes are on the order of 10 MeV. For the same reason, the
specific heat of the CFL phase is also dominated by the Goldstone modes.
Notwithstanding this, both the emissivity and the specific heat from the
massive modes remain rather small, because of their extremely small number
densities. The values of the emissivity and the specific heat imply that the
timescale for the cooling of the CFL core in isolation is y,
which makes the CFL phase invisible as the exterior layers of normal matter
surrounding the core will continue to cool through significantly more rapid
processes. If the CFL phase appears during the evolution of a proto-neutron
star, neutrino interactions with Goldstone bosons are expected to be
significantly more important since temperatures are high enough (
MeV) to admit large number densities of Goldstone modes.Comment: 29 pages, no figures. slightly modified text, one new eqn. and new
refs. adde
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