Instability of three dimensional conformally dressed black hole

The three dimensional black hole solution of Einstein equations with negative cosmological constant coupled to a conformal scalar field is proved to be unstable against linear circularly symmetric perturbations.Comment: 5 pages, REVTe

Power Spectrum of Cosmic Momentum Field Measured from the SFI Galaxy Sample

We have measured the cosmic momentum power spectrum from the peculiar velocities of galaxies in the SFI sample. The SFI catalog contains field spiral galaxies with radial peculiar velocities derived from the I-band Tully-Fisher relation. As a natural measure of the large-scale peculiar velocity field, we use the cosmic momentum field that is defined as the peculiar velocity field weighted by local number of galaxies. We have shown that the momentum power spectrum can be derived from the density power spectrum for the constant linear biasing of galaxy formation, which makes it possible to estimate \beta_S = \Omega_m^{0.6} / b_S parameter precisely where \Omega_m is the matter density parameter and b_S is the bias factor for optical spiral galaxies. At each wavenumber k we estimate \beta_S(k) as the ratio of the measured to the derived momentum power over a wide range of scales (0.026 h^{-1}Mpc <~ k <~ 0.157 h^{-1}Mpc) that spans the linear to the quasi-linear regimes. The estimated \beta_S(k)'s have stable values around 0.5, which demonstrates the constancy of \beta_S parameter at scales down to 40 h^{-1}Mpc. We have obtained \beta_S=0.49_{-0.05}^{+0.08} or \Omega_m = 0.30_{-0.05}^{+0.09} b_S^{5/3}, and the amplitude of mass fluctuation as \sigma_8\Omega_m^{0.6}=0.56_{-0.21}^{+0.27}. The 68% confidence limits include the cosmic variance. We have also estimated the mass density power spectrum. For example, at k=0.1047 h Mpc^{-1} (\lambda=60 h^{-1}Mpc) we measure \Omega_m^{1.2} P_{\delta}(k)=(2.51_{-0.94}^{+0.91})\times 10^3 (h^{-1}Mpc)^3, which is lower compared to the high-amplitude power spectra found from the previous maximum likelihood analyses of peculiar velocity samples like Mark III, SFI, and ENEAR.Comment: 12 pages, 9 figures, accepted for publication in Ap

Supernarrow spectral peaks near a kinetic phase transition in a driven, nonlinear micromechanical oscillator

We measure the spectral densities of fluctuations of an underdamped nonlinear micromechanical oscillator. By applying a sufficiently large periodic excitation, two stable dynamical states are obtained within a particular range of driving frequency. White noise is injected into the excitation, allowing the system to overcome the activation barrier and switch between the two states. While the oscillator predominately resides in one of the two states for most excitation frequencies, a narrow range of frequencies exist where the occupations of the two states are approximately equal. At these frequencies, the oscillator undergoes a kinetic phase transition that resembles the phase transition of thermal equilibrium systems. We observe a supernarrow peak in the power spectral densities of fluctuations of the oscillator. This peak is centered at the excitation frequency and arises as a result of noise-induced transitions between the two dynamical states.Comment: 4 pages, 4 figure

Gravastars and Black Holes of Anisotropic Dark Energy

Dynamical models of prototype gravastars made of anisotropic dark energy are constructed, in which an infinitely thin spherical shell of a perfect fluid with the equation of state $p = (1-\gamma)\sigma$ divides the whole spacetime into two regions, the internal region filled with a dark energy fluid, and the external Schwarzschild region. The models represent "bounded excursion" stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes. Here we show, for the first time in the literature, a model of gravastar and formation of black hole with both interior and thin shell constituted exclusively of dark energy. Besides, the sign of the parameter of anisotropy ($p_t - p_r$) seems to be relevant to the gravastar formation. The formation is favored when the tangential pressure is greater than the radial pressure, at least in the neighborhood of the isotropic case ($\omega=-1$).Comment: 16 pages, 8 figures. Accepted for publication in Gen. Rel. Gra

Tropospheric HO2 determination by FAGE

The detection efficiency is greatest at low pressures, where the subsequent removal of the HO product by the NO reagent (via HO + NO + M yields HONO + M) is relatively slow. Moreover, nozzle expansion of the air from ambient to low pressures produces a turbulent zone that assists in mixing the reagent with the sample. If the HO product is observed by laser-excited fluorescence, then the other advantages of low-pressure detection by FAGE (Fluorescence Assay with Gas Expansion) also apply. The FAGE instrumental response was calibrated to external HO2 by observing NO decay in the photolysis of HO-CH2O mixtures and by choosing conditions in which HO2 + NO is the only significant NO destruction path. HO2 was determined in urban air

Optimizing survival outcomes with post-remission therapy in acute myeloid leukemia.

Optimization of post-remission therapies to maintain complete remission and prevent relapse is a major challenge in treating patients with acute myeloid leukemia (AML). Monitoring patients for measurable residual disease (MRD) is helpful to identify those at risk for relapse. Hypomethylating agents are being investigated as post-remission therapy. Identification of recurrent genetic alterations that drive disease progression has enabled the design of new, personalized approaches to therapy for patients with AML. Emerging data suggest that targeted post-remission therapy, alone or in combination with chemotherapy, may improve outcomes. Results of ongoing clinical trials will further define potential clinical benefits

An Improved Private Mechanism for Small Databases

We study the problem of answering a workload of linear queries $\mathcal{Q}$, on a database of size at most $n = o(|\mathcal{Q}|)$ drawn from a universe $\mathcal{U}$ under the constraint of (approximate) differential privacy. Nikolov, Talwar, and Zhang~\cite{NTZ} proposed an efficient mechanism that, for any given $\mathcal{Q}$ and $n$, answers the queries with average error that is at most a factor polynomial in $\log |\mathcal{Q}|$ and $\log |\mathcal{U}|$ worse than the best possible. Here we improve on this guarantee and give a mechanism whose competitiveness ratio is at most polynomial in $\log n$ and $\log |\mathcal{U}|$, and has no dependence on $|\mathcal{Q}|$. Our mechanism is based on the projection mechanism of Nikolov, Talwar, and Zhang, but in place of an ad-hoc noise distribution, we use a distribution which is in a sense optimal for the projection mechanism, and analyze it using convex duality and the restricted invertibility principle.Comment: To appear in ICALP 2015, Track

Bolometric light curves of supernovae and post-explosion magnetic fields

The various effects leading to diversity in the bolometric light curves of supernovae are examined: nucleosynthesis, kinematic differences, ejected mass, degree of mixing, and configuration and intensity of the magnetic field are discussed. In Type Ia supernovae, a departure in the bolometric light curve from the full-trapping decline of $^{56}$Co can occur within the two and a half years after the explosion, depending on the evolutionary path followed by the WD during the accretion phase. If convection has developed in the WD core during the presupernova evolution, starting several thousand years before the explosion, a tangled magnetic field close to the equipartition value should have grown in the WD. Such an intense magnetic field would confine positrons where they originate from the $^{56}$Co decays, and preclude a strong departure from the full-trapping decline, as the supernova expands. This situation is expected to occur in C+O Chandrasekhar WDs as opposed to edge-lit detonated sub-Chandrasekhar WDs. If the pre-explosion magnetic field of the WD is less intense than 10$^{5-8}$G, a lack of confinement of the positrons emitted in the $^{56}$Co decay and a departure from full-trapping decline would occur. The time at which it takes place can provide estimates of the original magnetic field of the WD, its configuration, and also of the mass of the supernova ejecta. In SN 1991bg, the bolometric light curve suggests absence of a significant tangled magnetic field (intensity lower than $10^{3}$ G). Chandrasekhar-mass models do not reproduce the bolometric light curve of this supernova. For SN 1972E, on the contrary, there is evidence for a tangled configuration of the magnetic field and its light curve is well reproduced by a Chandrasekhar WD explosion.Comment: 54 pages, including 8 figures. To appear in Ap