On the Matter of the Dijkgraaf--Vafa Conjecture

With the aim of extending the gauge theory -- matrix model connection to more general matter representations, we prove that for various two-index tensors of the classical gauge groups, the perturbative contributions to the glueball superpotential reduce to matrix integrals. Contributing diagrams consist of certain combinations of spheres, disks, and projective planes, which we evaluate to four and five loop order. In the case of $Sp(N)$ with antisymmetric matter, independent results are obtained by computing the nonperturbative superpotential for $N=4,6$ and 8. Comparison with the Dijkgraaf-Vafa approach reveals agreement up to $N/2$ loops in matrix model perturbation theory, with disagreement setting in at $h=N/2+1$ loops, $h$ being the dual Coxeter number. At this order, the glueball superfield $S$ begins to obey nontrivial relations due to its underlying structure as a product of fermionic superfields. We therefore find a relatively simple example of an ${\cal N}=1$ gauge theory admitting a large $N$ expansion, whose dynamically generated superpotential differs from the one obtained in the matrix model approach.Comment: 20 pages, harvmac. v2: added comments and reference

Classifying supersymmetric solutions in 3D maximal supergravity

The work of MS was supported in part by Grant-in-Aid for Young Scientists (B) 24740159 from the Japan Society for the Promotion of Science (JSPS) 10.13039/501100001691. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM) 10.13039/ 501100003404, which is part of the Netherlands Organization for Scientific Research (NWO).The work of MS was supported in part by Grant-in-Aid for Young Scientists (B) 24740159 from the Japan Society for the Promotion of Science (JSPS) 10.13039/501100001691. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM) 10.13039/ 501100003404, which is part of the Netherlands Organization for Scientific Research (NWO).The work of MS was supported in part by Grant-in-Aid for Young Scientists (B) 24740159 from the Japan Society for the Promotion of Science (JSPS) 10.13039/501100001691. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM) 10.13039/ 501100003404, which is part of the Netherlands Organization for Scientific Research (NWO

Magnetic Tower Outflows from a Radial Wire Array Z-pinch

We present the first results of high energy density laboratory astrophysics experiments which explore the evolution of collimated outflows and jets driven by a toroidal magnetic field. The experiments are scalable to astrophysical flows in that critical dimensionless numbers such as the Mach number, the plasma beta and the magnetic Reynolds number are all in the astrophysically appropriate ranges. Our experiments use the MAGPIE pulsed power machine and allow us to explore the role of magnetic pressure in creating and collimating the outflow as well as showing the creation of a central jet within the broader outflow cavity. We show that currents flow along this jet and we observe its collimation to be enhanced by the additional hoop stresses associated with the generated toroidal field. Although at later times the jet column is observed to go unstable, the jet retains its collimation. We also present simulations of the magnetic jet evolution using our two-dimensional resistive magneto-hydrodynamic (MHD) laboratory code. We conclude with a discussion of the astrophysical relevance of the experiments and of the stability properties of the jet.Comment: Accepted by MNRAS. 17 pages without figures. Full version with figures can be found at http://www.pas.rochester.edu/~afrank/labastro/MF230rv.pd

The quantum structure of black holes

We give an elementary review of black holes in string theory. We discuss black hole entropy from string microstates and Hawking radiation from these states. We then review the structure of 2-charge microstates, and explore how `fractionation' can lead to quantum effects over macroscopic length scales of order the horizon radius.Comment: Review article, 58 pages, 2 figures; references added, note about topics covere

Perturbative instabilities in Horava gravity

We investigate the scalar and tensor perturbations in Horava gravity, with and without detailed balance, around a flat background. Once both types of perturbations are taken into account, it is revealed that the theory is plagued by ghost-like scalar instabilities in the range of parameters which would render it power-counting renormalizable, that cannot be overcome by simple tricks such as analytic continuation. Implementing a consistent flow between the UV and IR limits seems thus more challenging than initially presumed, regardless of whether the theory approaches General Relativity at low energies or not. Even in the phenomenologically viable parameter space, the tensor sector leads to additional potential problems, such as fine-tunings and super-luminal propagation.Comment: 21 pages, version published at Class. Quant. Gra

Laser-Shock Compression and Hugoniot Measurements of Liquid Hydrogen to 55 GPa

The principal Hugoniot for liquid hydrogen was obtained up to 55 GPa under laser-driven shock loading. Pressure and density of compressed hydrogen were determined by impedance-matching to a quartz standard. The shock temperature was independently measured from the brightness of the shock front. Hugoniot data of hydrogen provide a good benchmark to modern theories of condensed matter. The initial number density of liquid hydrogen is lower than that for liquid deuterium, and this results in shock compressed hydrogen having a higher compression and higher temperature than deuterium at the same shock pressure.Comment: 8 pages, 7 figures, 2 tables, accepted for publication in Physical Review

2D numerical study of the radiation influence on shock structure relevant to laboratory astrophysics

Radiative shocks are found in various astrophysical objects and particularly at different stages of stellar evolution. Studying radiative shocks, their topology, and thermodynamical properties is therefore a starting point to understanding their physical properties. This study has become possible with the development of large laser facilities, which has provided fresh impulse to laboratory astrophysics. We present the main characteristics of radiative shocks modeled using cylindrical simulations. We focus our discussion on the importance of multi-dimensional radiative-transfer effects on the shock topology and dynamics. We present results obtained with our code HERACLES for conditions corresponding to experiments already performed on laser installations. The multi-dimensional hydrodynamic code HERACLES is specially adapted to laboratory astrophysics experiments and to astrophysical situations where radiation and hydrodynamics are coupled. The importance of the ratio of the photon mean free path to the transverse extension of the shock is emphasized. We present how it is possible to achieve the stationary limit of these shocks in the laboratory and analyze the angular distribution of the radiative flux that may emerge from the walls of the shock tube. Implications of these studies for stellar accretion shocks are presented.Comment: 8 pages, 7 figures, accepted for publication in A&

The factorial structure of the mini mental state examination (MMSE) in Japanese dementia patients

<p>Abstract</p> <p>Background</p> <p>The Mini-Mental State Examination (MMSE) is one of the most commonly used instruments in the evaluation of global cognitive status. Few studies have investigated the relationship among its components in terms of factorial structure in Japanese individuals suffering from dementia. The aims of this study were: 1) to analyze the factorial structure of MMSE in Japanese dementia patients, 2) to clarify the MMSE static structure in identifying different cognitive profiles and understanding how these profiles are related to levels of dysfunction in subsets of dementia patients.</p> <p>Methods</p> <p>30,895 consecutive outpatients with dementia were evaluated. The 11 subtests composing the MMSE and the global MMSE score were analyzed. Factor analysis based on principal component analysis with Promax rotation was applied to the data representing the frequency of failures in each subtest as identified by the MMSE.</p> <p>Results</p> <p>Factor analysis identified three factors that explained approximately 44.57% of the total variance. The first factor, immediate memory, essentially constituted a simple index of the reading and writing subtests. The second factor, orientation and delayed recall, expressed the ability to handle new information. The third factor, working memory, was most closely related to the severity of dementia at the time of test administration.</p> <p>Conclusions</p> <p>Japanese dementia patients appear to develop difficulty handling new information in the early stages of their disease. This finding, and our finding that there is a factor associated with disease severity, suggest that understanding the specific factors related to subtest items, which underlie the total MMSE score may be useful to clinicians in planning interventions for Japanese patients in the early stages of dementia.</p

Magnetization study of RuSr2Y1.5Ce 0.5Cu2O10 (Ru-1222)

We have studied the magnetic properties of the non-superconducting RuSr2Ln1.5Ce0.5Cu2O10 (Ln=Y, Dy and Ho, Ru-1222) compounds synthesized under high pressure (6 Gpa) at elevated temperature. The materials become magnetically ordered at TM =152(2) K regardless of Ln. The wide ferromagnetic-like hysteresis loops which open at 5 K, close themselves around Tirr= 90-100 K and the remanent magnetizations (Mrem) and the coercive fields (HC) become zero. Surprisingly, at Tirr<T< TM a reappearance of the Mrem and HC (with a peak at 120-130 K) is observed for all three samples studied. For the non-magnetic Ln=Y compound, the extracted saturation moment at 5 K and the effective paramagnetic moment are is 0.75 and 2.05 mB /Ru, values which are close to the expected 1 mB and 1.73 mB respectively, for the low-spin state of Ru5+. We argue that the Ru-1222 system becomes (i) anti-ferromagnetically (AFM) ordered at TM. In this range a metamagnetic transition is induced by the applied field (ii). At Tirr < TM, weak-ferromagnetism (W-FM) is induced by the canting of the Ru moments.Comment: 15 pages of text with figure. Submitted to Phys. Rev.

Pseudochelin A, a siderophore of Pseudoalteromonas piscicida S2040

A new siderophore containing a 4,5-dihydroimidazole moiety was isolated from Pseudoalteromonas piscicida S2040 together with myxochelins A and B, alteramide A and its cycloaddition product, and bromo- and dibromoalterochromides. The structure of pseudochelin A was established by spectroscopic techniques including 2D NMR and MS/MS fragmentation data. In bioassays selected fractions of the crude extract of S2040 inhibited the opportunistic pathogen Pseudomonas aeruginosa. Pseudochelin A displayed siderophore activity in the chrome azurol S assay at concentrations higher than 50 μM, and showed weak activity against the fungus Aspergillus fumigatus, but did not display antibacterial, anti-inflammatory or anticonvulsant activity