The accretion disk in the post period-minimum cataclysmic variable SDSS J080434.20+510349.2

This study of SDSS0804 is primarily concerned with the double-hump shape in the light curve and its connection with the accretion disk in this bounce-back system. Time-resolved photometric and spectroscopic observations were obtained to analyze the behavior of the system between superoutbursts. A geometric model of a binary system containing a disk with two outer annuli spiral density waves was applied to explain the light curve and the Doppler tomography. Observations were carried out during 2008-2009, after the object's magnitude decreased to V~17.7(0.1) from the March 2006 eruption. The light curve clearly shows a sinusoid-like variability with a 0.07 mag amplitude and a 42.48 min periodicity, which is half of the orbital period of the system. In Sept. 2010, the system underwent yet another superoutburst and returned to its quiescent level by the beginning of 2012. This light curve once again showed a double-humps, but with a significantly smaller ~0.01mag amplitude. Other types of variability like a "mini-outburst" or SDSS1238-like features were not detected. Doppler tomograms, obtained from spectroscopic data during the same period of time, show a large accretion disk with uneven brightness, implying the presence of spiral waves. We constructed a geometric model of a bounce-back system containing two spiral density waves in the outer annuli of the disk to reproduce the observed light curves. The Doppler tomograms and the double-hump-shape light curves in quiescence can be explained by a model system containing a massive >0.7Msun white dwarf with a surface temperature of ~12000K, a late-type brown dwarf, and an accretion disk with two outer annuli spirals. According to this model, the accretion disk should be large, extending to the 2:1 resonance radius, and cool (~2500K). The inner parts of the disk should be optically thin in the continuum or totally void.Comment: 12 pages, 15 figures, accepted for publication in A&

Signals for New Spin-1 Resonances in Electroweak Gauge Boson Pair Production at the LHC

The mechanism of electroweak symmetry breaking (EWSB) will be directly scrutinized soon at the CERN Large Hadron Collider (LHC). We analyze the LHC potential to look for new vector bosons associated with the EWSB sector. We present a possible model independent approach to search for these new spin--1 resonances. We show that the analyses of the processes pp --> l^+ l^- Emiss_T, l^\pm j j Emiss_T, l^\pm l^+ l^- Emiss_T, and l^+ l^- j j (with l=e or \mu and j=jet) have a large reach at the LHC and can lead to the discovery or exclusion of many EWSB scenarios such as Higgsless models.Comment: 10 pages, 11 figure

Megawatt solar power systems for lunar surface operations

The work presented here shows that a solar power system can provide power on the order of one megawatt to a lunar base with a fairly high specific power. The main drawback to using solar power is still the high mass, and therefore, cost of supplying energy storage through the solar night. The use of cryogenic reactant storage in a fuel cell system, however, greatly reduces the total system mass over conventional energy storage schemes

Stellar density profile and mass of the Milky Way Bulge from VVV data

We present the first stellar density profile of the Milky Way bulge reaching latitude $b=0^\circ$. It is derived by counting red clump stars within the colour\--magnitude diagram constructed with the new PSF-fitting photometry from VISTA Variables in the V\'\i a L\'actea (VVV) survey data. The new stellar density map covers the area between $|l|\leq 10^\circ$ and $|b|\leq 4.5^\circ$ with unprecedented accuracy, allowing to establish a direct link between the stellar kinematics from the Giraffe Inner Bulge Spectroscopic Survey (GIBS) and the stellar mass density distribution. In particular, the location of the central velocity dispersion peak from GIBS matches a high overdensity in the VVV star count map. By scaling the total luminosity function (LF) obtained from all VVV fields to the LF from Zoccali et al.(2003), we obtain the first fully empirical estimate of the mass in stars and remnants of the Galactic bulge. The Milky Way bulge stellar mass within ($|b|<9.5^\circ$, $|l|<10^\circ$) is $2.0\pm0.3\times 10^{10}M_{\odot}$.Comment: 4 pages, 5 figures, accepted for publication on A&

Neutrino masses, cosmological bound and four zero Yukawa textures

Four zero neutrino Yukawa textures in a specified weak basis, combined with $\mu\tau$ symmetry and type-I seesaw, yield a highly constrained and predictive scheme. Two alternately viable $3\times3$ light neutrino Majorana mass matrices $m_{\nu A}/m_{\nu B}$ result with inverted/normal mass ordering. Neutrino masses, Majorana in character and predicted within definite ranges with laboratory and cosmological inputs, will have their sum probed cosmologically. The rate for $0\nu\beta\beta$ decay, though generally below the reach of planned experiments, could approach it in some parameter region. Departure from $\mu\tau$ symmetry due to RG evolution from a high scale and consequent CP violation, with a Jarlskog invariant whose magnitude could almost reach $6\times 10^{-3}$, are explored.Comment: Published versio

Neutrinos and the matter-antimatter asymmetry in the Universe

The discovery of neutrino oscillations provides a solid evidence for nonzero neutrino masses and leptonic mixing. The fact that neutrino masses are so tiny constitutes a puzzling problem in particle physics. From the theoretical viewpoint, the smallness of neutrino masses can be elegantly explained through the seesaw mechanism. Another challenging issue for particle physics and cosmology is the explanation of the matter-antimatter asymmetry observed in Nature. Among the viable mechanisms, leptogenesis is a simple and well-motivated framework. In this talk we briefly review these aspects, making emphasis on the possibility of linking neutrino physics to the cosmological baryon asymmetry originated from leptogenesis.Comment: 8 pages, 1 table, 1 figure; Based on talk given at the Symposium STARS2011, 1 - 4 May 2011, Havana, Cuba; to be published in the Proceeding

Unknowns after the SNO Charged-Current Measurement

We perform a model-independent analysis of solar neutrino flux rates including the recent charged-current measurement at the Sudbury Neutrino Observatory (SNO). We derive a universal sum rule involving SNO and SuperKamiokande rates, and show that the SNO neutral-current measurement can not fix the fraction of solar $\nu_e$ oscillating to sterile neutrinos. The large uncertainty in the SSM $^8$B flux impedes a determination of the sterile neutrino fraction.Comment: Version to appear in PRL; includes analysis with anticipated SNO NC measuremen

Entanglement of two qubits mediated by one-dimensional plasmonic waveguides

We investigate qubit-qubit entanglement mediated by plasmons supported by one-dimensional waveguides. We explore both the situation of spontaneous formation of entanglement from an unentangled state and the emergence of driven steady-state entanglement under continuous pumping. In both cases, we show that large values for the concurrence are attainable for qubit-qubit distances larger than the operating wavelength by using plasmonic waveguides that are currently available.Comment: 4 pages, 4 figures. Minor Changes. Journal Reference added. Highlighted in Physic

Electron wave-function spillover in self-assembled InAs/InP quantum wires

Charge confinement in InAs/InP self-assembled quantum wires is studied experimentally using photoluminescence in pulsed magnetic fields and theoretically using adiabatic theory within the effective-mass approximation, taking into account the strain in the samples. We show both experimentally and theoretically that, in spite of the large conduction band offset, the electron wave function is significantly spilled out of the wire in the wire height direction for thin wires. Furthermore, for a wire thickness of up to 8 monolayers, the electron spillover is inversely related to the wire height. These effects are due to the large zero point energy of the electron. As the wire becomes thicker, the decrease in confinement energy is reflected in a reduction of the electron wave-function extent