Supernova cosmology: legacy and future

The discovery of dark energy by the first generation of high-redshift supernova surveys has generated enormous interest beyond cosmology and has dramatic implications for fundamental physics. Distance measurements using supernova explosions are the most direct probes of the expansion history of the Universe, making them extremely useful tools to study the cosmic fabric and the properties of gravity at the largest scales. The past decade has seen the confirmation of the original results. Type Ia supernovae are among the leading techniques to obtain high-precision measurements of the dark energy equation of state parameter, and in the near future, its time dependence. The success of these efforts depends on our ability to understand a large number of effects, mostly of astrophysical nature, influencing the observed flux at Earth. The frontier now lies in understanding if the observed phenomenon is due to vacuum energy, albeit its unnatural density, or some exotic new physics. Future surveys will address the systematic effects with improved calibration procedures and provide thousands of supernovae for detailed studies.Comment: Invited review, Annual Review of Nuclear and Particle Science (submitted version

Middle Darriwilian conodont zones in the uppermost San Juan limestone and the lower member of the Las Aguaditas formation, central Precordillera of San Juan, Argentina

The geological province of Precordillera is located in western Argentina. It extends 450 km meridionally and 110 km from east to west (Fig. 1) (Furque and Cuerda, 1979). The Lower Paleozoic stratigraphy is characterized by a thick succession of Cambro-Ordovician limestones, which were deposited in platform environments and interdigitate with clastic slope deposits toward the west (Keller et al., 1993; Astini, 1995).Fil: Feltes, Nicolás Alexis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Albanesi, Guillermo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Bergström, S. M.. Ohio State University; Estados Unido

A specific brain structural basis for individual differences in reality monitoring.

Much recent interest has centered on understanding the relationship between brain structure variability and individual differences in cognition, but there has been little progress in identifying specific neuroanatomical bases of such individual differences. One cognitive ability that exhibits considerable variability in the healthy population is reality monitoring; the cognitive processes used to introspectively judge whether a memory came from an internal or external source (e.g., whether an event was imagined or actually occurred). Neuroimaging research has implicated the medial anterior prefrontal cortex (PFC) in reality monitoring, and here we sought to determine whether morphological variability in a specific anteromedial PFC brain structure, the paracingulate sulcus (PCS), might underlie performance. Fifty-three healthy volunteers were selected on the basis of MRI scans and classified into four groups according to presence or absence of the PCS in their left or right hemisphere. The group with absence of the PCS in both hemispheres showed significantly reduced reality monitoring performance and ability to introspect metacognitively about their performance when compared with other participants. Consistent with the prediction that sulcal absence might mean greater volume in the surrounding frontal gyri, voxel-based morphometry revealed a significant negative correlation between anterior PFC gray matter and reality monitoring performance. The findings provide evidence that individual differences in introspective abilities like reality monitoring may be associated with specific structural variability in the PFC

Antimatter production in supernova remnants

We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusion coefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Moreover, the obtained positron/electron ratio decreases with energy, while the antiproton/proton ratio rises at most by a factor of two above 10 GeV.Comment: 8 pages, 8 eps figures; extended version of arXiv:1004.1118; v2: minor corrections, matches published versio

Dark matter annihilation at the galactic center

If cold dark matter is present at the galactic center, as in current models of the dark halo, it is accreted by the central black hole into a dense spike. Particle dark matter then annihilates strongly inside the spike, making it a compact source of photons, electrons, positrons, protons, antiprotons, and neutrinos. The spike luminosity depends on the density profile of the inner halo: halos with finite cores have unnoticeable spikes, while halos with inner cusps may have spikes so bright that the absence of a detected neutrino signal from the galactic center already places interesting upper limits on the density slope of the inner halo. Future neutrino telescopes observing the galactic center could probe the inner structure of the dark halo, or indirectly find the nature of dark matter.Comment: 4 pages, 5 figure

Neutralino Annihilation into a Photon and a Z boson

A full one-loop calculation of neutralino S-wave annihilation into the $Z\gamma$ final state is performed in the minimal supersymmetric extension of the Standard Model. This process, like the similar one with two photons in the final state, may be of importance for the indirect detection of supersymmetric dark matter through the very narrow $\gamma$ ray line that would result from neutralino annihilations in the galactic halo. We give the complete analytical formulas for this loop-induced process and treat the case of a pure Higgsino as a first application of our expressions. Predictions for the gamma line flux are given for the halo model which is of the form suggested by Kravtsov et al. and for the profile proposed by Navarro, Frenk and White. For heavy neutralinos, the lines from $2\gamma$ and $Z\gamma$ would have indistiguishable energy in a realistic detector, making the fluxes add and facilitating discovery. For lighter neutralinos, the positions and relative strengths of the two lines would give valuable information on the nature of the supersymmetric dark matter particles.Comment: 19 pages, LaTeX, 6 eps figures. Some formulas corrected, improved discussion of halo models, results and conclusions unchanged. Version to appear in Phys. Rev.

Bioestratigrafía de conodontes y correlación global del Darriwiliano medio-Sandbiano inferior (Ordovícico) Formación Las Aguaditas, precordillera de San Juan, Argentina

En la Formación Las Aguaditas, en su sección tipo en la precordillera Argentina, se registraron conodontes del Darriwiliano medio al Sandbiano bajo. Se recuperaron un total de 9.974 especímenes de 46 muestras carbonáticas; estos representan 68 especies pertenecientes a 38 géneros. Se llevó a cabo un estudio bioestratigráfico para verificar la edad del intervalo que incluye el contacto entra las formaciones San Juan y Las Aguaditas. La presencia de taxones guía indican una edad darriwiliana media para este intervalo. Las siguientes biozonas fueron determinadas en el área de estudio: Zona de Lenodusvariabilis, con las subzonas de Periodongladysae y Paroistodushorridus, correspondientes al esquema establecido para la precordillera; las zonas de L.v ariabilis, Yangtzeplacognathuscrassusy la deE oplacognathuspseudoplanuscon la subzonas de Microzarkodinahagetiana y M.ozarkodella, y la Zona de Pygodusanserinus, según el esquema Báltico; la Zona de Periodonmacrodentatus, con las subzonas de Histiodellasinuosa,H.holodentatayH. cf. holodentata, y la Zona de P.zgierzensis con la subzona de H.kristinae que se correlaciona con el esquema norteamericano. Se reconoció una discontinuidad estratigráfica entre los miembros inferior y medio de la Formación Las Aguaditas. Esta comprende las zonas de Eoplacognathussuecicus y Pygodus serra, y la subzona inferior de la Zona de Pygodusanserinus. La variación en la diversidad de conodontes en la sección de estudio se corresponde con patrones de somerización y profundización, que a su vez son congruentes con los cambios en la litología. Luego de analizar la composición taxonómica de las muestras se reconocieron, de manera cuantitativa, tres asociaciones de conodontes: a) Asociación diversa de conodontes, b) Asociación de baja diversidad de conodontes, y c) Asociación de conodontes en fase de recuperación. Se propone aplicar para la precordillera central el esquema de biozonación de América del Norte debido a la afinidad de los taxones guía documentada, brindando una correlación intercontinental más precisa para el Ordovícico Medio a nivel global.Middle Darriwilian to lower Sandbian conodonts were recorded from the Las Aguaditas Formation at its type section in the Argentine Precordillera. A total of 9,974 conodont specimens were recovered from 46 carbonate samples, which represent 68 species of 38 genera. A biostratigraphic study verified a middle Darriwilian age for the interval spanning the contact between the San Juan and the Las Aguaditas formations. The following zones are determined in the study section: the Lenodusvariabilis Zone, with the Periodongladysae and Paroistodushorridus subzones following the Precordilleran scheme; the L.variabilis, Yangtzeplacognathuscrassus, and the Eoplacognathuspseudoplanuszones with the Microzarkodinahagetiana and M.ozarkodella subzones, and the Pygodusanserinus Zone, according to the Scandinavian scheme; the Periodonmacrodentatus Zone, with the Histiodellasinuosa,H.holodentata and H.cf. holodentatasubzones, and the P.zgierzensis Zone with the H.kristinae Subzone that correlates the North American scheme. A stratigraphic gap was recognized between the lower and middle members of the Las Aguaditas Formation. It comprises the Eoplacognathussuecicus and Pygodus serra zones, and the lower subzone of the PygodusanserinusZone. The variation of conodont diversity through the study section conforms to shallowing and deepening patterns, which accompanies the changes of the provenance lithology. Three conodont assemblages were quantitatively recognized: a) Diverse conodont association, b) Low diversity conodont association and c) Recovery phase association. We propose to use the North American biozonal scheme of conodonts for the Central Precordillera because of the affinity of documented index taxa, which provides a more accurate intercontinental correlation for the global Middle Ordovician Series.Fil: Feltes, Nicolás Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Albanesi, Guillermo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Bergström, S. M.. Ohio State University; Estados Unido

Two photon annihilation of Kaluza-Klein dark matter

We investigate the fermionic one-loop cross section for the two photon annihilation of Kaluza-Klein (KK) dark matter particles in a model of universal extra dimensions (UED). This process gives a nearly mono-energetic gamma-ray line with energy equal to the KK dark matter particle mass. We find that the cross section is large enough that if a continuum signature is detected, the energy distribution of gamma-rays should end at the particle mass with a peak that is visible for an energy resolution of the detector at the percent level. This would give an unmistakable signature of a dark matter origin of the gamma-rays, and a unique determination of the dark matter particle mass, which in the case studied should be around 800 GeV. Unlike the situation for supersymmetric models where the two-gamma peak may or may not be visible depending on parameters, this feature seems to be quite robust in UED models, and should be similar in other models where annihilation into fermions is not helicity suppressed. The observability of the signal still depends on largely unknown astrophysical parameters related to the structure of the dark matter halo. If the dark matter near the galactic center is adiabatically contracted by the central star cluster, or if the dark matter halo has substructure surviving tidal effects, prospects for detection look promising.Comment: 17 pages, 3 figures; slightly revised versio

Cross-correlations in scaling analyses of phase transitions

Thermal or finite-size scaling analyses of importance sampling Monte Carlo time series in the vicinity of phase transition points often combine different estimates for the same quantity, such as a critical exponent, with the intent to reduce statistical fluctuations. We point out that the origin of such estimates in the same time series results in often pronounced cross-correlations which are usually ignored even in high-precision studies, generically leading to significant underestimation of statistical fluctuations. We suggest to use a simple extension of the conventional analysis taking correlation effects into account, which leads to improved estimators with often substantially reduced statistical fluctuations at almost no extra cost in terms of computation time.Comment: 4 pages, RevTEX4, 3 tables, 1 figur

Antimatter and Gamma-rays from Dark Matter Annihilation

A brief review of the indirect detection signatures of dark matter is given. In particular, detection methods of dark matter particle annihilation to antimatter and gamma-rays are reviewed. With the GLAST satellite soon to be launched, a crucial window in the energy range of a few GeV up to 300 GeV will open. The good angular and energy resolution of the instrument means that structures predicted by cold dark matter models can be searched for. Large, currently planned ground-based imaging Cherenkov telescope arrays, may further improve the limits, or discover a signal, if the current understanding of halo dark matter structure is correct.Comment: 7p, one fig., invited talk at TAUP 2007, Sendai, Japan, to appear in the Proceeding