Mass estimate of the Swift J 164449.3+573451 supermassive black hole based on the 3:2 QPO resonance hypothesis

A dormant Swift source J 164449.3+573451 (Sw 164449+57)recently experienced a powerful outburst, caused most probably by a tidal disruption of a star by the super-massive black hole at the center of the source. During the outburst, a quasi periodic oscillation (QPO) was detected in the observed X-ray flux from Sw 164449+57. We show that if the observed QPO belongs to a "3:2 twin peak QPO" (with the second frequency not observed), the mass of the black hole in Sw 164449+57 is rather low, M ~ 10^5 M_sun, and the source belongs to a class of intermediate mass black holes. The low mass of the source has been pointed out previously by several authors.Comment: Accepted by Astronomy and Astrophysic

Precision Measurements of the Semileptonic Charm Decays D0→π−ℓ+νD^0 \to \pi^- \ell^+ \nu and D0→K−ℓ+νD^0 \to K^- \ell^+ \nu

We investigate the decays $D^0\to\pi^-\ell^+\nu$ and $D^0\to K^-\ell^+ \nu$, where $\ell$ is $e$ or $\mu$, using approximately 7 ${\rm fb}^{-1}$ of data collected with the CLEO III detector. We find $R_0\equiv {\cal B}(D^0\to \pi^-e^+\nu)/{\cal B}(D^0\to K^-e^+\nu)= 0.082 \pm 0.006 \pm 0.005$. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and $R_0$ gives $|f^{\pi}_{+}(0)|^2 |V_{cd}|^2/|f^K_{+}(0)|^2 |V_{cs}|^2 = 0.038^{+0.006+0.005}_{-0.007-0.003}$.Comment: 5 pages, 2 figures, talk given at DPF'04, UC Riverside, C

Particle Acceleration in Mildly Relativistic Shearing Flows: the Interplay of Systematic and Stochastic Effects, and the Origin of the Extended High-energy Emission in AGN Jets

The origin of the extended X-ray emission in the large-scale jets of active galactic nuclei (AGNs) poses challenges to conventional models of acceleration and emission. Although the electron synchrotron radiation is considered the most feasible radiation mechanism, the formation of the continuous large-scale X-ray structure remains an open issue. As astrophysical jets are expected to exhibit some turbulence and shearing motion, we here investigate the potential of shearing flows to facilitate an extended acceleration of particles and evaluate its impact on the resultant particle distribution. Our treatment incorporates systematic shear and stochastic second-order Fermi effects. We show that for typical parameters applicable to large-scale AGN jets, stochastic second-order Fermi acceleration, which always accompanies shear particle acceleration, can play an important role in facilitating the whole process of particle energization. We study the time-dependent evolution of the resultant particle distribution in the presence of second-order Fermi acceleration, shear acceleration, and synchrotron losses using a simple Fokker--Planck approach and provide illustrations for the possible emergence of a complex (multicomponent) particle energy distribution with different spectral branches. We present examples for typical parameters applicable to large-scale AGN jets, indicating the relevance of the underlying processes for understanding the extended X-ray emission and the origin of ultrahigh-energy cosmic rays.Comment: 26 pages, 8 figures; to appear in Ap

Proton-proton and deuteron-gold collisions at RHIC

We try to understand recent data on proton-proton and deuteron-gold collisions at RHIC, employing a modified parton model approach.Comment: Invited talk, given at the XXth Winter Workshop on Nuclear Dynamics, Trelawny Beach, Jamaica, March 200

N-representability is QMA-complete

We study the computational complexity of the N-representability problem in quantum chemistry. We show that this problem is QMA-complete, which is the quantum generalization of NP-complete. Our proof uses a simple mapping from spin systems to fermionic systems, as well as a convex optimization technique that reduces the problem of finding ground states to N-representability

Rotating Superconductors and the Frame-independent London Equation

A frame-independent, thermodynamically exact London equation is presented, which is especially valid for rotating superconductors. A direct result is the unexpectedly high accuracy ($\sim10^{-10}$) for the usual expression of the London moment.Comment: 4 pages, 0 figure

Development of stochastic models of window state changes in educational buildings

How people would like to interact with surrounding environment will subsequently influence indoor thermal conditions and further impact building energy performance. In order to understand occupants' adaptive behaviours in terms of environmental control utilization from the point of view of quantification, an investigation on windows operation was carried out in non-air-conditioned educational buildings in the UK during summer time considering the effects of occupant type (active and passive) and the time of a day. Outdoor air temperature was a better predictor or window operation than indoor air temperature. Window operation was found to be time-evolving event. The purpose or criteria of adjusting window states were different at different occupancy stages. Active occupants were more willing to change windows states in response to outdoor air temperature variations. Sub-models predicting transition probabilities of window state for different occupant type and occupancy stages were developed. The results derived from this field study are helpful with improving building simulation accuracy by integrating sub-models into simulation software and further providing guideline on building energy reduction without sacrificing indoor thermal comfort