Higher-order ratios of baryon number cumulants

The relevance of higher order cumulants of net baryon number fluctuations for the analysis of freeze-out and critical conditions in heavy-ion collisions at LHC and RHIC is addressed. The sign structure of the higher order cumulants in the vicinity of the chiral crossover temperature might be a sensitive probe and may allow to elucidate their relation to the QCD phase transition. We calculate ratios of generalized quark-number susceptibilities to high orders in three flavor QCD-like models and investigate their sign structure close to the chiral crossover line.Comment: presented at the International Conference "Critical Point and Onset of Deconfinement - CPOD 2011", Wuhan, November 7-11, 2011; version to appear in Cent. Eur. J. Phy

Heuristic Models of Two-Fermion Relativistic Systems with Field-Type Interaction

We use the chain of simple heuristic expedients to obtain perturbative and exactly solvable relativistic spectra for a family of two-fermionic bound systems with Coulomb-like interaction. In the case of electromagnetic interaction the spectrum coincides up to the second order in a coupling constant with that following from the quantum electrodynamics. Discrepancy occurs only for S-states which is the well-known difficulty in the bound-state problem. The confinement interaction is considered too. PACS number(s): 03.65.Pm, 03.65.Ge, 12.39.PnComment: 16 pages, LaTeX 2.0

Rate of Period Change as a Diagnostic of Cepheid Properties

Rate of period change $\dot{P}$ for a Cepheid is shown to be a parameter that is capable of indicating the instability strip crossing mode for individual objects, and, in conjunction with light amplitude, likely location within the instability strip. Observed rates of period change in over 200 Milky Way Cepheids are demonstrated to be in general agreement with predictions from stellar evolutionary models, although the sample also displays features that are inconsistent with some published models and indicative of the importance of additional factors not fully incorporated in models to date.Comment: Published in PASP (March 2006); TeX source & figures now provide

Anomalous Multiplicity Fluctuations from Phase Transitions in Heavy Ion Collisions

Event-by-event fluctuations and correlations between particles produced in relativistic nuclear collisions are studied. The fluctuations in positive, negative, total and net charge are closely related through correlations. In the event of a phase transitions to a quark-gluon plasma, fluctuations in total and net charge can be enhanced and reduced respectively which, however, is very sensitive to the acceptance and centrality. If the colliding system experiences strong density fluctuations due, e.g., to droplet formation in a first-order phase transition, all fluctuations can be enhanced substantially. The importance of fluctuations and correlations is exemplified by event-by-event measurement of the multiplicities of $J/\Psi$'s and charged particles since these observables should anti-correlate in the presence of co-mover or anomalous absorption.Comment: revised version to appear in Phys. Rev. C, 5 page

The OmegaWhite Survey for Short-Period Variable Stars IV: Discovery of the warm DQ white dwarf OW J175358.85-310728.9

We present the discovery and follow-up observations of the second known variable warm DQ white dwarf OW J175358.85-310728.9 (OW J1753-3107). OW J1753-3107 is the brightest of any of the currently known warm or hot DQ and was discovered in the OmegaWhite Survey as exhibiting optical variations on a period of 35.5452 (2) mins, with no evidence for other periods in its light curves. This period has remained constant over the last two years and a single-period sinusoidal model provides a good fit for all follow-up light curves. The spectrum consists of a very blue continuum with strong absorption lines of neutral and ionised carbon, a broad He I 4471 A line, and possibly weaker hydrogen lines. The C I lines are Zeeman split, and indicate the presence of a strong magnetic field. Using spectral Paschen-Back model descriptions, we determine that OW J1753-3107 exhibits the following physical parameters: T_eff = 15430 K, log(g) = 9.0, log(N(C)/N(He)) = -1.2, and the mean magnetic field strength is B_z =2.1 MG. This relatively low temperature and carbon abundance (compared to the expected properties of hot DQs) is similar to that seen in the other warm DQ SDSS J1036+6522. Although OW J1753-3107 appears to be a twin of SDSS J1036+6522, it exhibits a modulation on a period slightly longer than the dominant period in SDSS J1036+6522 and has a higher carbon abundance. The source of variations is uncertain, but they are believed to originate from the rotation of the magnetic white dwarf.Comment: 11 pages, 8 figures, 7 tables. Accepted for publication by MNRA

Searching for unknown open clusters in the Tycho-2 catalog

We present 11 new open cluster candidates found in a systematic search for unknown star clusters using the astrometric and photometric data included in the Tycho2 catalog. The possible existence of these stellar aggregates is supported by the analysis of proper motions, color-magnitude diagrams, stellar density distributions, and by the visual inspection of the Digitized Sky Survey (DSS) plates. With these tools we were able to determine mean absolute proper motions as well as preliminary reddenings, distances and ages for the majority of the candidates. We found that most of them are possibly nearby (closer than about 600 pc) open clusters never studied before.Comment: 14 pages, 6 figures. Accepted by A&

Hydrodynamical description of a hadron-quark first-order phase transition

Solutions of hydrodynamical equations are presented for the equation of state of the Var der Waals type allowing for the first order phase transition. Attention is focused on description of the hadron-quark phase transition in heavy ion collisions. It is shown that fluctuations dissolve and grow as if the fluid is effectively very viscous. Even in spinodal region germs are growing slowly due to viscosity and critical slowing down. This prevents enhancement of fluctuations in the near-critical region, which is frequently considered as a signal of the critical point in heavy ion collisions.Comment: 4 pages, 4 figure

Social and Cultural Dynamics in the Neolithic of Baikal-Yenisey Siberia: problems, hypotheses and facts

An assessment was made of the possibilities of using burial complexes to study social and cultural dynamics in the Neolithic of Baikal-Yenisey Siberia (~8.6–5 ka cal BP). The cultural-chronological scheme developed for the Middle Holocene of the Cis-Baikal as a result of the implementation of the Baikal Archaeological Project (BAP) is analyzed. It is concluded that the selective geographical coverage and insufficient attention to the materials of the campsites limited the possibilities of interpreting the BAP results and led to the creation of not quite correct periodization and the artificial phenomenon of hiatus, characterized by the absence of formal burials in the Middle Neolithic. The evolutionist approach of the BAP determined the nature of the concept, which implies a predominantly endogenous development of the Cis-Baikal cultures and does not take into account external factors. Based upon the correlation data of materials from burials and campsites of Baikal-Yenisey Siberia (which in the Neolithic was a single cultural area), the authors propose an alternative view of the dynamics of societies and cultures of local hunter-gatherers. According to it, there are four events that led to significant changes and three transitions, during which one or another cultural pattern was formed, have been identified. At the same time, the authors call for abandoning the use of the concept of “Late Mesolithic” for the beginning of Middle Holocene and propose to combine it with the Early Neolithic and we also make our proposals for filling the Middle Neolithic hiatus