Simple derivation of general Fierz-type identities

General Fierz-type identities are examined and their well known connection with completeness relations in matrix vector spaces is shown. In particular, I derive the chiral Fierz identities in a simple and systematic way by using a chiral basis for the complex $4\times4$ matrices. Other completeness relations for the fundamental representations of SU(N) algebras can be extracted using the same reasoning.Comment: 9pages. Few sentences modified in introduction and in conclusion. Typos corrected. An example added in introduction. Title modifie

Formation and Disruption of Cosmological Low Mass Objects

We investigate the evolution of cosmological low mass (low virial temperature) objects and the formation of the first luminous objects. First, the `cooling diagram' for low mass objects is shown. We assess the cooling rate taking into account the contribution of H_2, which is not in chemical equilibrium generally, with a simple argument of time scales. The reaction rates and the cooling rate of H_2 are taken from the recent results by Galli & Palla (1998). Using this cooling diagram, we also estimate the formation condition of luminous objects taking into account the supernova (SN) disruption of virialized clouds. We find that the mass of the first luminous object is several times 10^7 solar mass, because smaller objects may be disrupted by the SNe before they become luminous. Metal pollution of low mass (Ly-alpha) clouds also discussed. The resultant metallicity of the clouds is about 1/1000 of the solar metallicity.Comment: 11 pages, 2 figures, To appear in ApJ

Axion Like Particles and the Inverse Seesaw Mechanism

Light pseudoscalars known as axion like particles (ALPs) may be behind physical phenomena like the Universe transparency to ultra-energetic photons, the soft $\gamma$-ray excess from the Coma cluster, and the 3.5 keV line. We explore the connection of these particles with the inverse seesaw (ISS) mechanism for neutrino mass generation. We propose a very restrictive setting where the scalar field hosting the ALP is also responsible for generating the ISS mass scales through its vacuum expectation value on gravity induced nonrenormalizable operators. A discrete gauge symmetry protects the theory from the appearance of overly strong gravitational effects and discrete anomaly cancellation imposes strong constraints on the order of the group. The anomalous U$(1)$ symmetry leading to the ALP is an extended lepton number and the protective discrete symmetry can be always chosen as a subgroup of a combination of the lepton number and the baryon number.Comment: 29pp. v4: published version with erratum. Conclusions unchange

Formation of Primordial Protostars

The evolution of collapsing metal free protostellar clouds is investigated for various masses and initial conditions. We perform hydrodynamical calculations for spherically symmetric clouds taking account of radiative transfer of the molecular hydrogen lines and the continuum, as well as of chemistry of the molecular hydrogen. The collapse is found to proceed almost self-similarly like Larson-Penston similarity solution. In the course of the collapse, efficient three-body processes transform atomic hydrogen in an inner region of \sim 1 M_{\sun} entirely into molecular form. However, hydrogen in the outer part remains totally atomic although there is an intervening transitional layer of several solar masses, where hydrogen is in partially molecular form. No opaque transient core is formed although clouds become optically thick to H$_{2}$ collision-induced absorption continuum, since H$_{2}$ dissociation follows successively. When the central part of the cloud reaches stellar densities ($\sim 10^{-2} {\rm g cm^{-3}}$), a very small hydrostatic core (\sim 5 \times 10^{-3} M_{\sun}) is formed and subsequently grows in mass as the ambient gas accretes onto it. The mass accretion rate is estimated to be 3.7 \times 10^{-2} M_{\sun} {\rm yr^{-1}} (M_{\ast}/M_{\sun})^{-0.37}, where $M_{\ast}$ is instantaneous mass of the central core, by using a similarity solution which reproduces the evolution of the cloud before the core formation.Comment: 20 pages, 5 Postscript figures, uses AAS LaTe

Pacific 187Os/188Os isotope chemistry and U-Pb geochronology: synchroneity of global Os isotope change across OAE 2

Studies of OAE 2 sections beyond the Atlantic Ocean, Western Interior Seaway (WIS) and European pelagic shelf are limited. Here, we present initial osmium isotope stratigraphy (187Os/188Os–Osi) from two proto-Pacific sites that span the Cenomanian–Turonian boundary interval (CTBI): the Yezo Group (YG) section, Hokkaido, Japan, and the Great Valley Sequence (GVS), California, USA; to evaluate the 187Os/188Os seawater chemistry of the proto-Pacific. Additionally we combine new 206Pb/238U zircon CA-ID-TIMS geochronology from five volcanic tuff horizons of the Yezo Group section to test and facilitate inter-basinal integration with the WIS using radio-isotopically constrained age–depth models for both sections, and quantitatively constrain the absolute timing and duration of events across the CTBI. The YG shows an almost identical Osi profile to that of the WIS, and very similar to that of other sites of the proto-Atlantic and European pelagic oceans (Turgeon and Creaser, 2008 and Du Vivier et al., 2014). The characteristics of the Osi profile are radiogenic and heterogeneous (∼0.55–0.85) prior to the OAE 2, and synchronous with the inferred OAE 2 onset the Osi abruptly become unradiogenic and remain relatively homogeneous (∼0.20–0.30) before showing a gradual return to more radiogenic View the MathML source throughout the middle to late OAE 2. A206Pb/238U zircon age of an interbedded tuff (HK017) in the adjacent horizon to the first unradiogenic Osi value constrains the age of the Osi inflection at 94.44±0.14 Ma. This age, including uncertainty, agrees with the interpolated age of the same point in the Osi profile (94.28±0.25 Ma) in the only other dated OAE 2 section, the WIS; indicating a coeval shift in seawater chemistry associated with volcanism at the OAE 2 onset at the levels of temporal resolution (ca. 0.1 Myr). Further, prior to the onset of OAE 2 an enhanced radiogenic inflection in the Osi profile of the YG is correlative, within uncertainty, with a similar trend in the WIS based on the U–Pb age–depth model. The interpolated ages, 94.78±0.12 Ma and 94.66±0.25 Ma for this Osi inflection in the YG and WIS, respectively, indicate that palaeocirculation was sufficient to simultaneously influence transbasinal seawater chemistry. In contrast, the pre-OAE 2 Osi profile for the GVS is disparate to that of the YG and those of the proto-Atlantic and European pelagic shelf locations. We interpret the pre OAE 2 heterogeneous Osi values (0.30–0.95) to record a palaeobasin that was regionally influenced interchangeably by both unradiogenic (hydrothermal flux) and radiogenic (continental flux) Os. We conclude that the Osi profiles from the proto-Pacific sections record both trends that are consistent globally (OAE 2 onset, syn and post OAE 2), but also show regional differences (pre OAE 2) between OAE 2 sections worldwide. As such the Osi profiles coupled with U–Pb geochronology facilitate the correlation of OAE 2 stratigraphy, and demonstrate both regional and global ocean dynamics

Observations of Wood Bison Swimming across the Liard River, Northwest Territories, Canada

We observed a group of 18 wood bison, of mixed sex and age classes, swimming across a 1.7 km wide section of the Liard River on 16 July 2002. Water levels and flow rates were above the long-term average for that time of year, and there was a river current of 14-16 km/h. The animals took at least 27 minutes to negotiate their 3.6 km swim. Younger animals were able to keep more of their head and body above the water level than older mature males. Calves of the year, observed swimming across a secondary channel of the river on 15 July 2003, had only their heads above water. Bison are capable of swimming across lakes and rivers (Wood Buffalo National Park, Yellowstone National Park), but well-documented cases of bison navigating rapidly flowing northern rivers are rare. Open-water crossings of the Liard River are important to the ecology of the Nahanni wood bison population, especially since seismic activity in the Liard River Valley is likely to increase.Le 16 juillet 2002, on a observé un groupe de 18 bisons des bois, des deux sexes et de groupes d'âge divers, traversant à la nage une section de la rivière Liard large de 1,7 km. Le niveau d'eau et le débit fluvial dépassaient la moyenne à long terme pour cette période de l'année, et le courant fluvial y était de 14 à 16 km/h. Les animaux ont mis au moins 27 minutes pour négocier leur traversée de 3,6 km. Les plus jeunes pouvaient garder hors de l'eau une plus grande partie de leur tête et de leur corps que d'autres mâles plus âgés. Les veaux de l'année, que l'on a observés le 15 juillet 2003, durant leur traversée à la nage d'une branche secondaire de la rivière, n'avaient que la tête hors de l'eau. Les bisons sont capables de traverser des lacs et des rivières (parc national Wood Buffalo, parc national Yellowstone), mais on ne connaît que peu de cas bien documentés de bisons négociant la traversée de cours d'eau nordiques à courant rapide. La traversée des eaux libres de la Liard est importante pour l'écologie de la population du bison des bois de la Nahanni, en particulier si l'on considère que la prospection sismique va probablement augmenter dans la vallée de la Liard