HST - WFPC2 photometry of the globular cluster ngc 288: binary systems, blue stragglers and very blue stars

We report on new WFPC2 observations of the globular cluster NGC 288, focusing our attention on peculiar stars. A very pronounced binary sequence, paralleling the ordinary Main Sequence (MS) is clearly observed in the Color Magnitude Diagram (CMD) and a huge relative fraction of Blue Straggler Stars is measured. The dataset offers the opportunity of studying the evolution of a large population of binaries (and binary evolution by-products) in a low density environment, where the evolution of such systems is not dominated by collisions and encounters. Three (very) Extreme Horizontal Branch Stars have been found, all lying outside of the cluster core.Comment: 6 pages, 3 figures, in press in the chemical evolution of the Milky Way: stars versus clusters, F. Matteucci and F. Giovannelli eds, Kluwe

Distances from Surface Brightness Fluctuations

The practice of measuring galaxy distances from their spatial fluctuations in surface brightness is now a decade old. While several past articles have included some review material, this is the first intended as a comprehensive review of the surface brightness fluctuation (SBF) method. The method is conceptually quite simple, the basic idea being that nearby (but unresolved) star clusters and galaxies appear "bumpy", while more distant ones appear smooth. This is quantified via a measurement of the amplitude of the Poisson fluctuations in the number of unresolved stars encompassed by a CCD pixel (usually in an image of an elliptical galaxy). Here, we describe the technical details and difficulties involved in making SBF measurements, discuss theoretical and empirical calibrations of the method, and review the numerous applications of the method from the ground and space, in the optical and near-infrared. We include discussions of stellar population effects and the "universality" of the SBF standard candle. A final section considers the future of the method.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles', A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in press. 22 pages, including 3 postscript figures; uses Kluwer's crckapb.sty LaTex macro file, enclose

Distances from the Correlation between Galaxy Luminosities and Rotation Rates

A large luminosity--linewidth template sample is now available, improved absorption corrections have been derived, and there are a statistically significant number of galaxies with well determined distances to supply the zero point. A revised estimate of the Hubble Constant is H_0=77 +-4 km/s/Mpc where the error is the 95% probability statistical error. Systematic uncertainties are potentially twice as large.Comment: 21 pages, 9 figures. Invited chapter for the book `Post-Hipparcos Cosmic Candles', Eds. F. Caputo and A. Heck (Kluwer Academic Publishers, Dordrecht

Fundamental Strings, Holography, and Nonlinear Superconformal Algebras

We discuss aspects of holography in the AdS_3 \times S^p near string geometry of a collection of straight fundamental heterotic strings. We use anomalies and symmetries to determine general features of the dual CFT. The symmetries suggest the appearance of nonlinear superconformal algebras, and we show how these arise in the framework of holographic renormalization methods. The nonlinear algebras imply intricate formulas for the central charge, and we show that in the bulk these correspond to an infinite series of quantum gravity corrections. We also makes some comments on the worldsheet sigma-model for strings on AdS_3\times S^2, which is the holographic dual geometry of parallel heterotic strings in five dimensions.Comment: 25 page

The Hubble Constant

I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first uses individual astrophysical objects which have some property that allows their intrinsic luminosity or size to be determined, or allows the determination of their distance by geometric means. The second category comprises the use of all-sky cosmic microwave background, or correlations between large samples of galaxies, to determine information about the geometry of the Universe and hence the Hubble constant, typically in a combination with other cosmological parameters. Many, but not all, object-based measurements give $H_0$ values of around 72-74km/s/Mpc , with typical errors of 2-3km/s/Mpc. This is in mild discrepancy with CMB-based measurements, in particular those from the Planck satellite, which give values of 67-68km/s/Mpc and typical errors of 1-2km/s/Mpc. The size of the remaining systematics indicate that accuracy rather than precision is the remaining problem in a good determination of the Hubble constant. Whether a discrepancy exists, and whether new physics is needed to resolve it, depends on details of the systematics of the object-based methods, and also on the assumptions about other cosmological parameters and which datasets are combined in the case of the all-sky methods.Comment: Extensively revised and updated since the 2007 version: accepted by Living Reviews in Relativity as a major (2014) update of LRR 10, 4, 200

Scattering Theory and PT\mathcal{P}\mathcal{T}-Symmetry

We outline a global approach to scattering theory in one dimension that allows for the description of a large class of scattering systems and their $\mathcal{P}$-, $\mathcal{T}$-, and $\mathcal{P}\mathcal{T}$-symmetries. In particular, we review various relevant concepts such as Jost solutions, transfer and scattering matrices, reciprocity principle, unidirectional reflection and invisibility, and spectral singularities. We discuss in some detail the mathematical conditions that imply or forbid reciprocal transmission, reciprocal reflection, and the presence of spectral singularities and their time-reversal. We also derive generalized unitarity relations for time-reversal-invariant and $\mathcal{P}\mathcal{T}$-symmetric scattering systems, and explore the consequences of breaking them. The results reported here apply to the scattering systems defined by a real or complex local potential as well as those determined by energy-dependent potentials, nonlocal potentials, and general point interactions.Comment: Slightly expanded revised version, 38 page

A review of elliptical and disc galaxy structure, and modern scaling laws

A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their models to describe the radial distribution of stars in `nebulae'. This article reviews the progress since then, providing both an historical perspective and a contemporary review of the stellar structure of bulges, discs and elliptical galaxies. The quantification of galaxy nuclei, such as central mass deficits and excess nuclear light, plus the structure of dark matter halos and cD galaxy envelopes, are discussed. Issues pertaining to spiral galaxies including dust, bulge-to-disc ratios, bulgeless galaxies, bars and the identification of pseudobulges are also reviewed. An array of modern scaling relations involving sizes, luminosities, surface brightnesses and stellar concentrations are presented, many of which are shown to be curved. These 'redshift zero' relations not only quantify the behavior and nature of galaxies in the Universe today, but are the modern benchmark for evolutionary studies of galaxies, whether based on observations, N-body-simulations or semi-analytical modelling. For example, it is shown that some of the recently discovered compact elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to appear in "Planets, Stars and Stellar Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references incl. many somewhat forgotten, pioneer papers. Original submission to Springer: 07-June-201

Amygdaloid Kindling and the GABA System

The effect of increased brain GABA levels on fully kindled amygdala seizures was investigated in Long-Evans rats. The newly synthesized GABA-transaminase inhibitor, -Γ-acetylenic GABA (GAG) administered on four consecutive days (100 mg/kg, followed by 50 mg/kg, i.p.) was found to either significantly reduce, or eliminate entirely, the behavioral seizures normally produced by amygdala stimulation. The effect is seen after the first injection of GAG although its magnitude was greater on subsequent days. Behavioral seizures reappeared 2 to 3 days after termination of GAG treatment. The duration of electrographic seizures (self-sustained amygdala after-discharge) was either unchanged or greater on the first day of GAG treatment, but was briefer on subsequent days. The duration of afterdischarges returned to normal levels 1 to 2 days earlier than the behavioral seizures after the termination of GAG. Picrotoxin (1.5-2 mg/kg, i.p.) did not antagonize either electrographic or behavioral effects of inhibition produced with GAG. Electrical stimulation of amygdala delivered during the initial sedation stage induced by picrotoxin resulted in further regression of kindled seizures in the majority of animals. Although in doses employed, GAG alleviates amygdaloid-kindled seizures its use requires caution in view of its ability to reduce arousal level. RÉSUMÉ L'effet de l'ÉlÉvation des taux cÉrÉbraux de GABA sur les crises amygdaliennes par effet d'embrasement complet a ÉtÉÉtudiÉ chez des rats Long-Evans. l'injection pendant 4 jours consÉcutifs de 100 mg/kg suivis de 50 mg/kg i.p. d'un inhibiteur de la GABA. Transaminase nouvellement synthÉtisÉ (Γ-acetylenic GABA ou GAG) a significativement rÉduit ou mÊme supprimÉ les crises normalement provoquÉes par la stimulation amygdalienne. l'effet est observÉ aprÈs la premiere injection de GAG, mais son importance s'accroit les jours suivants. Les crises rÉapparaissent 2 ou 3 jours aprÈs la fin du traitement au GAG. Du point de vue Électrographique, la durÉe de la postdÉcharge amygdalienne autoentretenue est inchingÉe ou accrue le premier jour du traitement, mais elle diminue les jours suivants pour retourner À la normale un ou deux jours avant que les crises ne rÉapparaissent aprÈs la fin de ('administration du GAG. l'injection de picrotoxine (1.5-2 mg/kg i.p.) ne s'oppose pas aux effets inhibiteurs du GAG sur les crises ou leur accompagnement EEG. La stimulation Électrique de l'amygdala pendant l'Étape sÉdative initiate induite par la picrotoxine provoque une rÉgression supplÉmentaire des crises d'embrasement chez la majoritÉ des animaux. Bien que, aux doses utilisÉes, le GAG attÉnue les crises amyg-daliennes d'embrasement, son utilisation nÉcessite des prÉcautions compte tenu de sa tendance À rÉduire le niveau d'Éveil. RESUMEN En ratas Long-Evans se ha investigado el efecto del aumento de los niveles cerebrales de GABA, sobre los ataques originados en la amÍgdala totalmente condicionada, (Kindling). El recientemente sintetizado in-hibidor de la GABA transaminasa, Γ-acetilÉnico GABA (GAG), redujo significativamente o eliminÓ totalmente las crisis de comportamiento que habitualmente se producen con la estimulaciÓn de la amÍgdala. El efecto se observa despuÉs de la primera in-yecciÓn de GAG pero su magnitud aumentÓ en dias subsiguientes. Las crisis de comportamiento reaparecieron a los 2–3 dÍas de la interrupciÓn del tratamiento con GAG. La duraciÓn de los ataques electrogrÁficos (perservaciÓn de la post-descarga de la amigdala) no se modificÓ, o incluso aumentÓ, en el primer dia de la administraciÓn de GAG pero se redujo en los dias siguientes. La duraciÓn de las post-descargas volviÓ a sus niveles normales 1 o 2 dias antes que la reapariciÓn de las crisis de comportamiento una vez terminado el tratamiento con GAG. La picrotoxina (1.5-2 mg/kg, i.p.) no antagonizÓ los efectos inhibitorios producidos por el GAG sobre el electroencefalograma o las crisis de comportamiento. La estimulaciÓn elÉctrica sobre la amÍgdala, aplicada durante la fase de sedaciÓn inicial inducida por la picrotoxina, condujo a una regresiÓn aÚn mÁs intensa de las crisis condicionadas, en la mayorÍa de los animales. A pesar de que, con las dosis utilizadas, el GAG alivia las crisis de la amÍgdala previamente condicionada, se requiere gran precauciÓn en su utilizaciÓn en vista de su propiedad de reducir el nivel del despertar. ZUSAMMENFASSUNG Die Wirkung erhÖhter GABA-Spiegel des Gehirns auf AmygdalonkrÄmpfe nach Kindling wurden bei Long-Evans-Ratten untersucht. Der neuerdings synthetisierte GABA-TYansaminasen-Inhibitor, Gamma-Acetylen-GABA (GAG) wurde an 4 aufeinander-folgenden Tagen in einer Dosis von 100 mg/kg und anschlieliend 50 mg/kg i.p. verabfolgt. Er reduzierte entweder signifikant oder eliminierte vÖllig die anfalls-weisen VerhaltensÄnderungen, die normalerweise durch Stimulation des Amygdalon produziert wurden. Die Wirkung ist nach der Erstinjektion des GAG zu beobachten, obgleich ihr Ausmaß an folgenden Tagen grÖßer war. Die VerhaltensanfÄlle kamen 2 bis 3 Tagen nach Beendigung der GAG-Behandlung wieder. Die Dauer der elektrographischen AnfÄlle (sich selbst un-terhaltende Amydalonnachentladungen) blieben entweder gleich oder sie wurden grÖßer am 1. Tag der GAG-Behandlung, wurden aber kÜrzer an folgenden Tagen. Die Dauer der Nachentladungen nor-malisierte sich 1 bis 2 Tage frÜher als die VerhaltensanfÄlle nach Beendigung des GAG verschwanden. Picrotoxin (1.5 bis 2 mg/kg i.p.) wirken nicht als Antagonist gegenÜber der durch GAG produzierten Hemmung der elektrographischen-oder Verhalten-seffekte. Die elektrische Stimulierung des Amygdalon wÄhrend der initialen Sedierung nach Picrotoxin ver-ursachte bei der Mehrzahl der Tiere einen weiteren RÜckgang der durch Kindling entstandenen AnfÄlle. Obgleich das GAG in den verwandten Dosen, die durch Kindling des Amygdalon erzeugten KrÄmpfe leichter ablaufen lUßt, erfordert seine Anwendung Vorsicht hinsichtlich seiner FÄhigkeit, das Erreg-barkeitsniveau zu senken.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66112/1/j.1528-1157.1980.tb04058.x.pd

Rν\nuMDM and Lepton Flavor Violation

A model relating radiative seesaw and minimal dark matter mass scales without beyond the standard model (SM) gauge symmetry (R$\nu$MDM) is constructed. In addition to the SM particles, the R$\nu$MDM contains, a Majorana fermion multiplet $N_R$ and scalar multiplet $\chi$ that transform respectively as $(1,5,0)$ and $(1,6,-1/2)$ under the SM gauge group $SU(3)_C\times SU(2)_L\times U(1)_Y$. The neutral component $N_R^0$ plays the role of dark matter with a mass in the range of 9 to 10 TeV. This scale also sets the lower limit for the scale for the heavy degrees of freedom in $N_R$ and $\chi$ which generate light neutrino masses through the radiative seesaw mechanism. The model predicts an $N_R^0$-nucleus scattering cross section that would be accessible with future dark matter direct detection searches as well as observable effects in present and searches for charged lepton flavor violating processes, such as $l_i\to l_j \gamma$ and $\mu - e$ conversion.Comment: Latex 18 pages with 7 figures. Discussions added in dark matter section and a few references adde