r-Java 2.0: the nuclear physics

[Aims:] We present r-Java 2.0, a nucleosynthesis code for open use that performs r-process calculations as well as a suite of other analysis tools. [Methods:] Equipped with a straightforward graphical user interface, r-Java 2.0 is capable of; simulating nuclear statistical equilibrium (NSE), calculating r-process abundances for a wide range of input parameters and astrophysical environments, computing the mass fragmentation from neutron-induced fission as well as the study of individual nucleosynthesis processes. [Results:] In this paper we discuss enhancements made to this version of r-Java, paramount of which is the ability to solve the full reaction network. The sophisticated fission methodology incorporated into r-Java 2.0 which includes three fission channels (beta-delayed, neutron-induced and spontaneous fission) as well as computation of the mass fragmentation is compared to the upper limit on mass fission approximation. The effects of including beta-delayed neutron emission on r-process yield is studied. The role of coulomb interactions in NSE abundances is shown to be significant, supporting previous findings. A comparative analysis was undertaken during the development of r-Java 2.0 whereby we reproduced the results found in literature from three other r-process codes. This code is capable of simulating the physical environment of; the high-entropy wind around a proto-neutron star, the ejecta from a neutron star merger or the relativistic ejecta from a quark nova. As well the users of r-Java 2.0 are given the freedom to define a custom environment. This software provides an even platform for comparison of different proposed r-process sites and is available for download from the website of the Quark-Nova Project: http://quarknova.ucalgary.ca/Comment: 26 pages, 18 figures, 1 tabl

Quark Matter in Neutron Stars: An apercu

The existence of deconfined quark matter in the superdense interior of neutron stars is a key question that has drawn considerable attention over the past few decades. Quark matter can comprise an arbitrary fraction of the star, from 0 for a pure neutron star to 1 for a pure quark star, depending on the equation of state of matter at high density. From an astrophysical viewpoint, these two extreme cases are generally expected to manifest different observational signatures. An intermediate fraction implies a hybrid star, where the interior consists of mixed or homogeneous phases of quark and nuclear matter, depending on surface and Coulomb energy costs, as well as other finite size and screening effects. In this brief review article, we discuss what we can deduce about quark matter in neutron stars in light of recent exciting developments in neutron star observations. We state the theoretical ideas underlying the equation of state of dense quark matter, including color superconducting quark matter. We also highlight recent advances stemming from re-examination of an old paradigm for the surface structure of quark stars and discuss possible evolutionary scenarios from neutron stars to quark stars, with emphasis on astrophysical observations.Comment: 15 pages, 1 figure. Invited review for Modern Physics Letters

Constraining phases of quark matter with studies of r-mode damping in neutron stars

The r-mode instability in rotating compact stars is used to constrain the phase of matter at high density. The color-flavor-locked phase with kaon condensation (CFL-K0) and without (CFL) is considered in the temperature range 10^8K < T <10^{11} K. While the bulk viscosity in either phase is only effective at damping the r-mode at temperatures T > 10^{11} K, the shear viscosity in the CFL-K0 phase is the only effective damping agent all the way down to temperatures T > 10^8 K characteristic of cooling neutron stars. However, it cannot keep the star from becoming unstable to gravitational wave emission for rotation frequencies f ~ 56-11 Hz at T ~ 10^8-10^9 K. Stars composed almost entirely of CFL or CFL-K0 matter are ruled out by observation of rapidly rotating neutron stars, indicating that dissipation at the quark-hadron interface or nuclear crust interface must play a key role in damping the instability.Comment: 8 pages, 2 figure

High-density Skyrmion matter and Neutron Stars

We examine neutron star properties based on a model of dense matter composed of B=1 skyrmions immersed in a mesonic mean field background. The model realizes spontaneous chiral symmetry breaking non-linearly and incorporates scale-breaking of QCD through a dilaton VEV that also affects the mean fields. Quartic self-interactions among the vector mesons are introduced on grounds of naturalness in the corresponding effective field theory. Within a plausible range of the quartic couplings, the model generates neutron star masses and radii that are consistent with a preponderance of observational constraints, including recent ones that point to the existence of relatively massive neutron stars with mass M 1.7 Msun and radius R (12-14) km. If the existence of neutron stars with such dimensions is confirmed, matter at supra-nuclear density is stiffer than extrapolations of most microscopic models suggest.Comment: 27 pages, 5 figures, AASTeX style; to be published in The Astrophysical Journa

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 $B\sim 10^{13}$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 $r$-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

Numerical Simulation of the Hydrodynamical Combustion to Strange Quark Matter

We present results from a numerical solution to the burning of neutron matter inside a cold neutron star into stable (u,d,s) quark matter. Our method solves hydrodynamical flow equations in 1D with neutrino emission from weak equilibrating reactions, and strange quark diffusion across the burning front. We also include entropy change due to heat released in forming the stable quark phase. Our numerical results suggest burning front laminar speeds of 0.002-0.04 times the speed of light, much faster than previous estimates derived using only a reactive-diffusive description. Analytic solutions to hydrodynamical jump conditions with a temperature dependent equation of state agree very well with our numerical findings for fluid velocities. The most important effect of neutrino cooling is that the conversion front stalls at lower density (below approximately 2 times saturation density). In a 2-dimensional setting, such rapid speeds and neutrino cooling may allow for a flame wrinkle instability to develop, possibly leading to detonation.Comment: 5 pages, 3 figures (animations online at http://www.capca.ucalgary.ca/~bniebergal/webPHP/research.php

Efficacy of Clofibrate with Phototherapy VS Phototherapy in Neonatal Hyperbilirubinemia: A Randomised Controlled Trial

INTRODUCTION: Hyperbilirubinemia is yellow discolouration of sclera, skin and mucosa with elevated concentration of serum bilirubin. Neonates appear jaundiced if serum bilirubin exceeds 5 to 7 mg/dl (86-119 micro mol/l). Approximately 85% of term newborn and almost all preterm newborn develop clinical jaundice. Chemical hyperbilirubinemia is serum bilirubin greater than 2mg /dl, which is universal in all newborns. According to Maisels and Gifford21 97 centile bilirubin for all healthy term newborn is 12.4 mg/dl for formula fed infants and 14.8 mg/dl in breast fed newborns. Any serum bilirubin exceeding 17 mg/dl is pathologic and warrants investigation for cause. Visual assessment of severity of serum bilirubin is done by Kramer rule . There is a cephalocaudal progression of jaundice due to maximal perfusion of face, then trunk and lastly the limbs. Apart from this the affinity of binding of albumin and bilirubin varies with distance from heart for blood in circulatory system. Jaundice in head and neck quantitates to 4 -8 mg/dl, upper trunk 5-12 mg/dl, lower trunk and thigh 8-16 mg/dl and palms and soles quantitates to greater than 15 mg/dl. This method is not reliable as examination needs bright day light and interpretation in dark skinned individuals is difficult. Factors making newborn prone for hyperbilirubinemiaare : 1. Increased bilirubinproduction, 2. less effective binding and transportation, 3. less efficient conjugation andexcretion and 4. Increased enterohepatic circulation. Source of bilirubin production are RBC hemoglobin where 1 gram hemoglobin produces 34 mg bilirubin, and 25% bilirubin called Early Labelled Bilirubin produced from ineffective erythropoiesis in bone marrow and other heme containing proteins.AIMS AND OBJECTIVES OF THE STUDY: To assess the efficacy of clofibrate with phototherapy versus Phototherapy in treatment of neonatal hyperbilirubinemia Outcomes measured: 1. peak bilirubin 2. duration of phototheraphy 3. need of exchange transfusion RESEARCH HYPOTHESIS: Adjunctive usage of clofibrate with phototherapy reduces the duration of phototherapy, reduces the occurrence of failure of phototherapy by induction of enzyme glucuronyl transferase and prevents the rise of serum bilirubin during phototherapy treatment. DISCUSSION: Neonatal jaundice is a common clinical entity with common occurrence between 25 hours and 144 hours in 70% -80 % of term newborns and of these 20 % to 30% of newborn need phototherapy. Management of neonatal jaundice was revolutionized by use of phototherapy which has reduced the need of exchange transfusion and sequlae of bilirubin induced brain damage. Despite this effective therapy there is still difficulty in bringing down duration of phototherapy and there is still need of exchange transfusion in cases of hemolytic jaundice. This calls for need of adjunctive therapy to overcome these shortcomings in phototherapy. Clofibrate proposed to help in these avenues was tried in this clinical entity in the later part of twentieth century . Studies earlier tried clofibrate for non hemolytic jaundice. It is now studied to be useful in cases of hemolytic jaundice. This study had equal sex distribution and distribution of blood group incompatibility in either group. There were 55.55% of male babies in overall and this substantiates the fact male sex is a risk factor for neonatal hyperbilirubinemia2 .In a study by Hamid et al there was 55.6% of male babies in overall enrolled in the study with 57.8% and 53.3% of babies in clofibrate and control group respectively, substantiating our observation of increased incidence of hyperbilirubinemia in male sex. Sharafi et al in their study group had 42 % of babies were male sex and 58 % babies female sex in contrary to our observation of more male babies in our study. Sakha et al in their study had 62 % of male babies and 38 % female babies and this study was in concurrence with our observation of increased babies of male sex. CONCLUSION: Neonatal jaundice is a common entity with effective therapy in the form of phototherapy, but still the duration of phototherapy is quite prolonged affecting maternal and infant bonding. To reduce the duration of phototherapy adjunctive drugs has been tried . In this process clofibrate has come a long way and in this study it has reduced the duration of phototherapy by significant duration. There was no adverse effect during its use. Clofibrate is effective in lowering bilirubin at single low dose of 25 mg/kg at start of phototherapy. To support the use of this drug further studies on safety with long term follow up and use in sick term babies and stable preterm babies are needed

Photon Emission from Dense Quark Matter

Thermal emission rates and mean free paths of photons in a color-flavor locked (CFL) phase of quark matter at high densities and moderate temperatures are evaluated. Our calculations are based on a low-energy effective theory for CFL matter describing Goldstone boson excitations and their electromagnetic as well as strong interactions. In-medium coupling strengths of vector mesons are found to be smaller than in vacuum. As a consequence of in-medium modified pion dispersion relations, novel processes such as pi+ pi- -> gamma and gamma -> pi+ pi- become possible. The total photon emissivity is found to be very large, exceeding contributions from thermal e+ e- annihilation above temperatures of about 5 MeV. At the same time, the corresponding mean free paths become very small. Our results imply that the photon flux from the surface of a (hypothetical) CFL star in its early hot stages saturates the black-body limit. Estimates for the early thermal evolution of the star are also presented.Comment: 20 pages latex, 5 figures; v2: Figs.1 + 2 corrected, references added, minor revisions in text, conclusions unchanged, to appear in Nucl. Phys.