On the appearance of hyperons in neutron stars

By employing a recently constructed hyperon-nucleon potential the equation of state of \beta-equilibrated and charge neutral nucleonic matter is calculated. The hyperon-nucleon potential is a low-momentum potential which is obtained within a renormalization group framework. Based on the Hartree-Fock approximation at zero temperature the densities at which hyperons appear in neutron stars are estimated. For several different bare hyperon-nucleon potentials and a wide range of nuclear matter parameters it is found that hyperons in neutron stars are always present. These findings have profound consequences for the mass and radius of neutron stars.Comment: 12 pages, 12 figures, RevTeX4; summary and conclusions are strengthened, to appear in PR

Selfgravitating Gas Spheres in a Box and Relativistic Clusters: Relation between Dynamical and Thermodynamical Stability

We derive a variational principle for the dynamical stability of a cluster as a gas sphere in a box. Newtonian clusters are always dynamically stable and, for relativistic clusters, the relation between dynamical and thermodynamical instabilities is analyzed. The boundaries between dynamically and thermodynamically stable and unstable models are found numerically for relativistic stellar systems with different cut off parameters. A criterion based on binding energy curve is used for determination of the boundary of dynamical stability.Comment: 10 figure

Hyperons in a relativistic mean-field approach to asymmetric nuclear matter

Relativistic mean-field theory with $\delta$ meson, nonlinear isoscalar self-interactions and isoscalar-isovector cross interaction terms with parametrizations obtained to reproduce Dirac-Brueckner-Hartree-Fock calculations for nuclear matter is used to study asymmetric nuclear matter properties in $\beta$-equilibrium, including hyperon degrees of freedom and (hidden) strange mesons. Influence of cross interaction on composition of hyperon matter and electron chemical potential is examined. Softening of nuclear equation of state by the cross interactions results in lowering of hyperonization, although simultaneously enhancing a hyperon-induced decrease of the electron chemical potential, thus indicating further shift of a kaon condensate occurence to higher densities.Comment: 11 pages, 7 figures, 3 tables, published in Phys. Rev.

Inverse spectral problems for Sturm-Liouville operators with singular potentials

The inverse spectral problem is solved for the class of Sturm-Liouville operators with singular real-valued potentials from the space $W^{-1}_2(0,1)$. The potential is recovered via the eigenvalues and the corresponding norming constants. The reconstruction algorithm is presented and its stability proved. Also, the set of all possible spectral data is explicitly described and the isospectral sets are characterized.Comment: Submitted to Inverse Problem

How strange are compact star interiors ?

We discuss a Nambu--Jona-Lasinio (NJL) type quantum field theoretical approach to the quark matter equation of state with color superconductivity and construct hybrid star models on this basis. It has recently been demonstrated that with increasing baryon density, the different quark flavors may occur sequentially, starting with down-quarks only, before the second light quark flavor and at highest densities also the strange quark flavor appears. We find that color superconducting phases are favorable over non-superconducting ones which entails consequences for thermodynamic and transport properties of hybrid star matter. In particular, for NJL-type models no strange quark matter phases can occur in compact star interiors due to mechanical instability against gravitational collapse, unless a sufficiently strong flavor mixing as provided by the Kobayashi-Maskawa-'t Hooft determinant interaction is present in the model. We discuss observational data on mass-radius relationships of compact stars which can put constraints on the properties of dense matter equation of state.Comment: 7 pages, 2 figures, to appear in the Proceedings of the International Conference SQM2009, Buzios, Rio de Janeiro, Brazil, Sep.27-Oct.2, 200

Клинико-морфологические доказательства влияния консервантов на поверхность глаза при первичной открытоугольной глаукоме

PURPOSE: To compare clinical features related to changes in the eye surface caused by long term use of prostaglandin antiglaucoma agents, containing and not containing preservatives, and to perform comparative morphological analysis of the conjunctival biopsies in the study groups. METHODS: The study was performed on 90 patients aged 36 to 89 years (mean age 64.5±11.3 years), including 36 males and 54 females. The first two groups were comprised of the patients with newly diagnosed primary open-angle glaucoma stage 1-3, who were prescribed Taflotan without preservatives produced by «Santen» (tafluprost 0.0015% solution in single use 0.3 ml dripping tubes) (1st group) and 0.005% latanoprost with 0.02% benzalkonium chloride or 0.004% travoprost with 0.015% benzalkonium chloride (2nd group). Mean duration of treatment within the frameworks of the study was 135 days, minimal - 90 days. The control group included patients with age-related cataract of various degree of maturation who did not receive local treatment. In the beginning and the end of the study, all patients underwent assessment of the eye surface condition for Dry Eye Syndrome (DES), including symptom scope according to the OSDI (Ocular Surface Disease Index); assessment of the conjunctival folds degree (LIPCOF); the tear film rapture time (TFRT); the degree of Rose Bengal staining of the eye surface (RB); and Schirmer 1 test. At the end of the study selective biopsies were performed during the surgery. RESULTS: Statistically significant gender differences in DES incidence were revealed: 78% of females (42/54) versus 39% of males (14/36). At the end of the study statistically significant decrease in OSDI score in both groups was revealed, compared to baseline data without differences between the groups, as well as Schirmer 1 test in the second group. Treatment complications (hyperemia, subcompensated intraocular pressure, DES and cataract progression) were noted in 3 eyes in the first group, and 11 eyes in the second group (the difference was statistically significant). Hyperemia was revealed in 6% (2 eyes) and 17% (6 eyes), in the first and second group, respectively. In the second group DES progression was revealed, showing correlation with decreased tear expression during Schirmer 1 test. CONCLUSION: Tafluprost without preservatives is an effective and safe hypotensive agent from the group of prostaglandin analogues. It is better tolerated, causes least complaints during instillation, and less adverse effects in the long term use (hyperemia, advancement of the preexisting Dry Eye Syndrome, etc.) when compared to other medications from the same pharmacologic group containing preservatives, which is confirmed by comparative morphological assessment of conjunctiva biopsies.ЦЕЛЬ. Сравнить клинические проявления изменения поверхности глаза, связанные с длительным применением антиглаукомных препаратов простагландинового ряда, содержащих и не содержащих консервант, провести сравнительный морфологический анализ биоптатов конъюнктивы в исследуемых группах. методы. в іриняло участие 90 паци ентов в возрасте от 35 до 89 лет (64,5±11,3 года), из них 36 мужчин и 54 женщины. Первые две группы составили пациенты с впервые выявленной первичной открытоугольной глаукомой (ПОУГ) I-III стадий, которым были назначены тафлотан без консерванта, фирмы «Santen» (0,0015% тафлупрост в одноразовых тюбиках-капельницах по 0,3 мл) (1-я группа) и 0,005% латанопрост с 0,02% бензалкония хлоридом или 0,004% травопрост с 0,015% бензалкония хлоридом (2-я группа). Средняя длительность лечения в рамках исследования составила 135 дней, минимальная - 90 дней. Контрольная группа состояла из пациентов с возрастной катарактой различной степени зрелости, не получавших местной терапии. Всем пациентам в начале и в конце исследования проведена оценка состояния поверхности глаза на наличие синдрома «сухого глаза» (ССГ), включавшая жалобы по опроснику OSDI (Ocular Surface Disease Index), определение степени конъюнктивальных складок (LIPCOF), времени разрыва слезной пленки (ВРСП), степени окрашивания глазной поверхности бенгальским розовым (БР), теста Ширмера 1. Выборочно в конце исследования во время выполнения хирургического лечения взяты биоптаты конъюнктивы для морфологического исследования. РЕЗУЛЬТАТЫ. Выя значимые ген дерные различия частоты встречаемости ССГ: у 78% женщин (42/54) и у 39% мужчин (14/36). В конце исследования отмечено статистически значимое снижение баллов OSDI в обеих группах по сравнению со стартовыми данными без межгрупповых различий, а также теста Ширмера 1 во 2-й группе. Осложнения лечения (гиперемия, увеличение стадии ССГ и прогрессирование катаракты) отмечены в трех глазах в 1-й группе и в 11 глазах во 2-й группе (разница статистически значима). В группах гиперемия отмечена у 6% (2 глаза) и 17% (6 глаз) соответственно. Во 2-й группе выявлено усиление стадии ССГ, коррелирующее со снижением теста Ширмера 1. ЗАКЛЮЧЕНИЕ. Тафлупрост без консерванта является эффективным и безопасным гипотензивным препаратом из ряда аналогов простагландинов. Он лучше переносится, вызывая наименьшее количество жалоб во время инстилляции, а при длительном применении - меньшие побочные эффекты (гиперемия, усиление имеющегося ССГ и др.) по сравнению с другими препаратами аналогичной фармакологической группы, содержащими консервант, что подтверждает и сравнительное морфологическое исследование биоптатов конъюнктивы

An Exact General-Relativity Solution for the Motion and Intersections of Self-Gravitating Shells in the Field of a Massive Black Hole

The motion with intersections of relativistic gravitating shells in the Schwarzschild gravitational field of a central body is considered. Formulas are derived for calculating parameters of the shells after intersection via their parameters before intersection. Such special cases as the Newtonian approximation, intersections of light shells, and intersections of a test shell with a gravitating shell are also considered. The ejection of one of the shells to infinity in the relativistic region is described. The equations of motion for the shells are analyzed numerically.Comment: 21 pages, 8 figure

Periodic Pattern in the Residual-Velocity Field of OB Associations

An analysis of the residual-velocity field of OB associations within 3 kpc of the Sun has revealed periodic variations in the radial residual velocities along the Galactic radius vector with a typical scale length of lambda=2.0(+/-0.2) kpc and a mean amplitude of fR=7(+/-1) km/s. The fact that the radial residual velocities of almost all OB-associations in rich stellar-gas complexes are directed toward the Galactic center suggests that the solar neighborhood under consideration is within the corotation radius. The azimuthal-velocity field exhibits a distinct periodic pattern in the region 0<l<180 degrees, where the mean azimuthal-velocity amplitude is ft=6(+/-2) km/s. There is no periodic pattern of the azimuthal-velocity field in the region 180<l<360 degrees. The locations of the Cygnus arm, as well as the Perseus arm, inferred from an analysis of the radial- and azimuthal-velocity fields coincide. The periodic patterns of the residual-velocity fields of Cepheids and OB associations share many common features.Comment: 21 page

The Role of Strangeness in Astrophysics - an Odyssey through Strange Phases

The equation of state for compact stars is reviewed with special emphasis on the role of strange hadrons, strange dibaryons and strange quark matter. Implications for the properties of compact stars are presented. The importance of neutron star data to constrain the properties of hypothetic particles and the possible existence of exotic phases in dense matter is outlined. We also discuss the growing interplay between astrophysics and heavy-ion physics.Comment: invited talk given at Strange Quark Matter 2001, Frankfurt, Germany, 8 pages, uses iopart.cls, minor modifications, version to appear in J. Phys.

Stellar structure and compact objects before 1940: Towards relativistic astrophysics

Since the mid-1920s, different strands of research used stars as "physics laboratories" for investigating the nature of matter under extreme densities and pressures, impossible to realize on Earth. To trace this process this paper is following the evolution of the concept of a dense core in stars, which was important both for an understanding of stellar evolution and as a testing ground for the fast-evolving field of nuclear physics. In spite of the divide between physicists and astrophysicists, some key actors working in the cross-fertilized soil of overlapping but different scientific cultures formulated models and tentative theories that gradually evolved into more realistic and structured astrophysical objects. These investigations culminated in the first contact with general relativity in 1939, when J. Robert Oppenheimer and his students George Volkoff and Hartland Snyder systematically applied the theory to the dense core of a collapsing neutron star. This pioneering application of Einstein's theory to an astrophysical compact object can be regarded as a milestone in the path eventually leading to the emergence of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal