Pan-STARRS1 Discovery of Two Ultraluminous Supernovae at z ≈ 0.9

We present the discovery of two ultraluminous supernovae (SNe) at z ≈ 0.9 with the Pan-STARRS1 Medium Deep Survey. These SNe, PS1-10ky and PS1-10awh, are among the most luminous SNe ever discovered, comparable to the unusual transients SN 2005ap and SCP 06F6. Like SN 2005ap and SCP 06F6, they show characteristic high luminosities (M_(bol) ≈ –22.5 mag), blue spectra with a few broad absorption lines, and no evidence for H or He. We have constructed a full multi-color light curve sensitive to the peak of the spectral energy distribution in the rest-frame ultraviolet, and we have obtained time series spectroscopy for these SNe. Given the similarities between the SNe, we combine their light curves to estimate a total radiated energy over the course of explosion of (0.9-1.4) × 10^(51) erg. We find photospheric velocities of 12,000-19,000 km s^(–1) with no evidence for deceleration measured across ~3 rest-frame weeks around light curve peak, consistent with the expansion of an optically thick massive shell of material. We show that, consistent with findings for other ultraluminous SNe in this class, radioactive decay is not sufficient to power PS1-10ky, and we discuss two plausible origins for these events: the initial spin-down of a newborn magnetar in a core-collapse SN, or SN shock breakout from the dense circumstellar wind surrounding a Wolf-Rayet star

Supernova 2009kf: An Ultraviolet Bright Type IIP Supernova Discovered with Pan-STARRS 1 and GALEX

We present photometric and spectroscopic observations of a luminous Type IIP Supernova (SN) 2009kf discovered by the Pan-STARRS 1 (PS1) survey and also detected by the Galaxy Evolution Explorer. The SN shows a plateau in its optical and bolometric light curves, lasting approximately 70 days in the rest frame, with an absolute magnitude of M_V = -18.4 mag. The P-Cygni profiles of hydrogen indicate expansion velocities of 9000 km s^(-1) at 61 days after discovery which is extremely high for a Type IIP SN. SN 2009kf is also remarkably bright in the near-ultraviolet (NUV) and shows a slow evolution 10-20 days after optical discovery. The NUV and optical luminosity at these epochs can be modeled with a blackbody with a hot effective temperature (T ~ 16,000 K) and a large radius (R ~ 1 × 10^(15) cm). The bright bolometric and NUV luminosity, the light curve peak and plateau duration, the high velocities, and temperatures suggest that 2009kf is a Type IIP SN powered by a larger than normal explosion energy. Recently discovered high-z SNe (0.7 < z < 2.3) have been assumed to be IIn SNe, with the bright UV luminosities due to the interaction of SN ejecta with a dense circumstellar medium. UV-bright SNe similar to SN 2009kf could also account for these high-z events, and its absolute magnitude M_(NUV) = -21.5 ± 0.5 mag suggests such SNe could be discovered out to z ~ 2.5 in the PS1 survey

Improved electromechanical master-slave manipulator

Electric master-slave manipulator uses force multiplication and allows the operator to remotely control the slave arm. Both the master and slave arms execute seven distinct motions by a specially designed force-reflecting servo having a one to one correspondence between the motion at the master and slave

Resting state correlates of subdimensions of anxious affect

Resting state fMRI may help identify markers of risk for affective disorder. Given the comorbidity of anxiety and depressive disorders and the heterogeneity of these disorders as defined by DSM, an important challenge is to identify alterations in resting state brain connectivity uniquely associated with distinct profiles of negative affect. The current study aimed to address this by identifying differences in brain connectivity specifically linked to cognitive and physiological profiles of anxiety, controlling for depressed affect. We adopted a two-stage multivariate approach. Hierarchical clustering was used to independently identify dimensions of negative affective style and resting state brain networks. Combining the clustering results, we examined individual differences in resting state connectivity uniquely associated with subdimensions of anxious affect, controlling for depressed affect. Physiological and cognitive subdimensions of anxious affect were identified. Physiological anxiety was associated with widespread alterations in insula connectivity, including decreased connectivity between insula subregions and between the insula and other medial frontal and subcortical networks. This is consistent with the insula facilitating communication between medial frontal and subcortical regions to enable control of physiological affective states. Meanwhile, increased connectivity within a frontoparietal-posterior cingulate cortex-precunous network was specifically associated with cognitive anxiety, potentially reflecting increased spontaneous negative cognition (e.g., worry). These findings suggest that physiological and cognitive anxiety comprise subdimensions of anxiety-related affect and reveal associated alterations in brain connectivity

Apparent hysteresis in a driven system with self-organized drag

Interaction between extended defects and impurities lies at the heart of many physical phenomena in materials science. Here we revisit the ubiquitous problem of the driven motion of an extended defect in a field of mobile impurities, which self-organize to cause drag on the defect. Under a wide range of external conditions (e.g. drive), the defect undergoes a transition from slow to fast motion. This transition is commonly hysteretic: the defect either moves slow or fast, depending on the initial condition. We explore such hysteresis via a kinetic Monte Carlo spin simulation combined with computational coarse-graining. Obtaining bifurcation diagrams (stable and unstable branches), we map behavior regimes in parameter space. Estimating fast-slow switching times, we determine whether a simulation or experiment will exhibit hysteresis depending on observation conditions. We believe our approach is applicable to quantifying hysteresis in a wide range of physical contexts.Comment: 11 pages (preprint format), 4 color figures in separate file

1/f spectrum and memory function analysis of solvation dynamics in a room-temperature ionic liquid

To understand the non-exponential relaxation associated with solvation dynamics in the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate, we study power spectra of the fluctuating Franck-Condon energy gap of a diatomic probe solute via molecular dynamics simulations. Results show 1/f dependence in a wide frequency range over 2 to 3 decades, indicating distributed relaxation times. We analyze the memory function and solvation time in the framework of the generalized Langevin equation using a simple model description for the power spectrum. It is found that the crossover frequency toward the white noise plateau is directly related to the time scale for the memory function and thus the solvation time. Specifically, the low crossover frequency observed in the ionic liquid leads to a slowly-decaying tail in its memory function and long solvation time. By contrast, acetonitrile characterized by a high crossover frequency and (near) absence of 1/f behavior in its power spectra shows fast relaxation of the memory function and single-exponential decay of solvation dynamics in the long-time regime.Comment: 10 pages, 4 figure

A Reanalysis of the Hydrodynamic Theory of Fluid, Polar-Ordered Flocks

I reanalyze the hydrodynamic theory of fluid, polar ordered flocks. I find new linear terms in the hydrodynamic equations which slightly modify the anisotropy, but not the scaling, of the damping of sound modes. I also find that the nonlinearities allowed {\it in equilibrium} do not stabilize long ranged order in spatial dimensions $d=2$; in accord with the Mermin-Wagner theorem. Nonequilibrium nonlinearities {\it do} stabilize long ranged order in $d=2$, as argued by earlier work. Some of these were missed by earlier work; it is unclear whether or not they change the scaling exponents in $d=2$.Comment: 6 pages, no figures. arXiv admin note: text overlap with arXiv:0909.195

A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations

We report the results of our third survey for formaldehyde (H2CO) 6cm maser emission in the Galaxy. Using the Very Large Array, we detected two new H2CO maser sources (G23.01-0.41 and G25.83-0.18), thus increasing the sample of known H2CO maser regions in the Galaxy to seven. We review the characteristics of the G23.01-0.41 and G25.83-0.18 star forming regions. The H2CO masers in G23.01-0.41 and G25.83-0.18 share several properties with the other known H2CO masers, in particular, emission from rich maser environments and close proximity to very young massive stellar objects.Comment: Accepted for publication in the Astrophysical Journal Supplement Serie

Finite Temperature Spectral Densities of Momentum and R-Charge Correlators in N=4\N=4 Yang Mills Theory

We compute spectral densities of momentum and R-charge correlators in thermal $\N=4$ Yang Mills at strong coupling using the AdS/CFT correspondence. For $\omega \sim T$ and smaller, the spectral density differs markedly from perturbation theory; there is no kinetic theory peak. For large $\omega$, the spectral density oscillates around the zero-temperature result with an exponentially decreasing amplitude. Contrast this with QCD where the spectral density of the current-current correlator approaches the zero temperature result like $(T/\omega)^4$. Despite these marked differences with perturbation theory, in Euclidean space-time the correlators differ by only $\sim 10$ from the free result. The implications for Lattice QCD measurements of transport are discussed.Comment: 18 pages, 3 figure