Entanglement, BEC, and superfluid-like behavior of two-mode photon systems

A system of two interacting photon modes, without constraints on the photon number, in the presence of a Kerr nonlinearity, exhibits BEC if the transfer amplitude is greater than the mode frequency. A symmetry-breaking field (SBF) can be introduced by taking into account a classical electron current. The ground state, in the limit of small nonlinearity, becomes a squeezed state, and thus the modes become entangled. The smaller is the SBF, the greater is entanglement. Superfluid-like behavior is observed in the study of entanglement growth from an initial coherent state, since in the short-time range the growth does not depend on the SBF amplitude, and on the initial state amplitude. On the other hand, the latter is the only parameter which determines entanglement in the absence of the SBF

The Mid-Infrared Spectral Energy Distribution, Surface Brightness and Color Profiles in Elliptical Galaxies

We describe photometry at mid-infrared passbands (1.2 - 24 microns) for a sample of 18 elliptical galaxies. All surface brightness distributions resemble de Vaucouleurs profiles, indicating that most of the emission arises from the photospheres or circumstellar regions of red giant stars. The spectral energy distribution peaks near 1.6 microns, but the half-light or effective radius has a pronounced minimum near the K band (2.15 microns). Apart from the 24 micron passband, all sample-averaged radial color profiles have measurable slopes within about twice the (K band) effective radius. Evidently this variation arises because of an increase in stellar metallicity toward the galactic cores. For example, the sampled-averaged color profile (K - 5.8 microns) has a positive slope although no obvious absorption feature is observed in spectra of elliptical galaxies near 5.8 microns. This, and the minimum in the effective radius, suggests that the K band may be anomalously luminous in metal-rich stars in galaxy cores. Unusual radial color profiles involving the 24 micron passband may suggest that some 24 micron emission comes from interstellar not circumstellar dust grains.Comment: 18 pages. Accepted by Ap

Teleportation on a quantum dot array

We present a model of quantum teleportation protocol based on a double quantum dot array. The unknown qubit is encoded using a pair of quantum dots, coupled by tunneling, with one excess electron. It is shown how to create maximally entangled states with this kind of qubits using an adiabatically increasing Coulomb repulsion between different pairs. This entangled states are exploited to perform teleportation again using an adiabatic coupling between them and the incoming unknown state. Finally, a sudden separation of Bob's qubit enables a time evolution of Alice's state providing a modified version of standard Bell measurement. Substituting the four quantum dots entangled state with a chain of coupled DQD's, a quantum channel with high fidelity arises from this scheme allowing the transmission over long distances.Comment: 4 pages, 2 figure

Hot gaseous atmospheres in galaxy groups and clusters are both heated and cooled by X-ray cavities

Expanding X-ray cavities observed in hot gas atmospheres of many galaxy groups and clusters generate shock waves and turbulence that are primary heating mechanisms required to avoid uninhibited radiatively cooling flows which are not observed. However, we show here that the evolution of buoyant cavities also stimulates radiative cooling of observable masses of low-temperature gas. During their early evolution, radiative cooling occurs in the wakes of buoyant cavities in two locations: in thin radial filaments parallel to the buoyant velocity and more broadly in gas compressed beneath rising cavities. Radiation from these sustained compressions removes entropy from the hot gas. Gas experiencing the largest entropy loss cools first, followed by gas with progressively less entropy loss. Most cooling occurs at late times, $\sim 10^8-10^9$ yrs, long after the X-ray cavities have disrupted and are impossible to detect. During these late times, slightly denser low entropy gas sinks slowly toward the centers of the hot atmospheres where it cools intermittently, forming clouds near the cluster center. Single cavities of energy $10^{57}-10^{58}$ ergs in the atmosphere of the NGC 5044 group create $10^8 - 10^9$ $M_{\odot}$ of cooled gas, exceeding the mass of extended molecular gas currently observed in that group. The cooled gas clouds we compute share many attributes with molecular clouds recently observed in NGC 5044 with ALMA: self-gravitationally unbound, dust-free, quasi-randomly distributed within a few kpc around the group center.Comment: 12 pages, 11 figure; accepted for publication by Ap

Lepton asymmetry and primordial nucleosynthesis in the era of precision cosmology

We calculate and display the primordial light-element abundances as a function of a neutrino degeneracy parameter \xi common to all flavors. It is the only unknown parameter characterizing the thermal medium at the primordial nucleosynthesis epoch. The observed primordial helium abundance Y_p is the most sensitive cosmic ``leptometer.'' Adopting the conservative Y_p error analysis of Olive and Skillman implies -0.04 \alt \xi \alt 0.07 whereas the errors stated by Izotov and Thuan imply \xi=0.0245+-0.0092 (1 sigma). Improved determinations of the baryon abundance have no significant impact on this situation. A determination of Y_p that reliably distinguishes between a vanishing or nonvanishing \xi is a crucial test of the cosmological standard assumption that sphaleron effects equilibrate the cosmic lepton and baryon asymmetries.Comment: 5 pages, 2 figures; minor changes, references added, replaced to match the published version in PRD (Brief Reports

Detecting Axion-Like Particles With Gamma Ray Telescopes

We propose that axion-like particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma ray sources. This occurs as a result of gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the "Hillas criterion", such as jets of active galactic nuclei or hot spots of radio galaxies. The discovery of such an effect is possible by GLAST in the 1-100 GeV range and by ground based gamma ray telescopes in the TeV range.Comment: corrected typos, one plot modified, material rearranged for clarification. Conclusions unchanged. Matches version published in Phys. Rev. Let