Cross-Correlation Studies with CMB Polarization Maps

The free-electron population during the reionized epoch rescatters CMB temperature quadrupole and generates a now well-known polarization signal at large angular scales. While this contribution has been detected in the temperature-polarization cross power spectrum measured with WMAP data, due to the large cosmic variance associated with anisotropy measurements at tens of degree angular scales only limited information related to reionization, such as the optical depth to electron scattering, can be extracted. The inhomogeneities in the free-electron population lead to an additional secondary polarization anisotropy contribution at arcminute scales. While the fluctuation amplitude, relative to dominant primordial fluctuations, is small, we suggest that a cross-correlation between arcminute scale CMB polarization data and a tracer field of the high redshift universe, such as through fluctuations captured by the 21 cm neutral Hydrogen background or those in the infrared background related to first proto-galaxies, may allow one to study additional details related to reionization. For this purpose, we discuss an optimized higher order correlation measurement, in the form of a three-point function, including information from large angular scale CMB temperature anisotropies in addition to arcminute scale polarization signal related to inhomogeneous reionization. We suggest that the proposed bispectrum can be measured with a substantial signal-to-noise ratio and does not require all-sky maps of CMB polarization or that of the tracer field. A measurement such as the one proposed may allow one to establish the epoch when CMB polarization related to reionization is generated and to address if the universe was reionized once or twice.Comment: 13 pages, 7 figures; Version in press with Phys. Rev.

Localized surface states in HTSC: Alternative mechanism of zero-bias conductance peaks

It is shown that the quasiparticle states localized in the vicinity of surface imperfections of atomic size can be responsible for the zero-bias tunneling conductance peaks in high-Tc superconductors. The contribution from these states can be easily separated from other mechanisms using their qualitatively different response on an external magnetic field.Comment: REVTeX, 4 pages, 2 figs; to be published in PR

Evolution of the Schr\"odinger--Newton system for a self--gravitating scalar field

Using numerical techniques, we study the collapse of a scalar field configuration in the Newtonian limit of the spherically symmetric Einstein--Klein--Gordon (EKG) system, which results in the so called Schr\"odinger--Newton (SN) set of equations. We present the numerical code developed to evolve the SN system and topics related, like equilibrium configurations and boundary conditions. Also, we analyze the evolution of different initial configurations and the physical quantities associated to them. In particular, we readdress the issue of the gravitational cooling mechanism for Newtonian systems and find that all systems settle down onto a 0--node equilibrium configuration.Comment: RevTex file, 19 pages, 26 eps figures. Minor changes, matches version to appear in PR

Magnetoresistance and electronic structure of asymmetric GaAs/AlGaAs double quantum wells in the in-plane/tilted magnetic field

Bilayer two-dimensional electron systems formed by a thin barrier in the GaAs buffer of a standard heterostructure were investigated by magnetotransport measurements. In magnetic fields oriented parallel to the electron layers, the magnetoresistance exhibits an oscillation associated with the depopulation of the higher occupied subband and the field-induced transition into a decoupled bilayer. Shubnikov-de Haas oscillations in slightly tilted magnetic fields allow to reconstruct the evolution of the electron concentration in the individual subbands as a function of the in-plane magnetic field. The characteristics of the system derived experimentally are in quantitative agreement with numerical self-consistent-field calculations of the electronic structure.Comment: 6 pages, 5 figure

Andreev Bound States at the Interface of Antiferromagnets and d-wave Superconductors

We set up a simple transfer matrix formalism to study the existence of bound states at interfaces and in junctions between antiferromagnets and d-wave superconductors. The well-studied zero energy mode at the {110} interface between an insulator and a d-wave superconductor is spin split when the insulator is an antiferromagnet. This has as a consequence that any competing interface induced superconducting order parameter that breaks the time reversal symmetry needs to exceed a critical value before a charge current is induced along the interface.Comment: 4 pages, 3 figure

Measurement of Trace I-129 Concentrations in CsI Powder and Organic Liquid Scintillator with Accelerator Mass Spectrometry

Levels of trace radiopurity in active detector materials is a subject of major concern in low-background experiments. Procedures were devised to measure trace concentrations of I-129 in the inorganic salt CsI as well as in organic liquid scintillator with Accelerator Mass Spectrometry (AMS) which leads to improvement in sensitivities by several orders of magnitude over other methods. No evidence of their existence in these materials were observed. Limits of < 6 X 10^{-13} g/g and < 2.6 X 10^{-17} g/g on the contaminations of I-129 in CsI and liquid scintillator, respectively, were derived.These are the first results in a research program whose goals are to develop techniques to measure trace radioactivity in detector materials by AMS.Comment: Proceedings of 10th International Conference on Accelerator Mass Spectrometr

Cosmological distance indicators

We review three distance measurement techniques beyond the local universe: (1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and (3) HI intensity mapping. We describe the principles and theory behind each method, the ingredients needed for measuring such distances, the current observational results, and future prospects. Time delays from strongly lensed quasars currently provide constraints on $H_0$ with < 4% uncertainty, and with 1% within reach from ongoing surveys and efforts. Recent exciting discoveries of strongly lensed supernovae hold great promise for time-delay cosmography. BAO features have been detected in redshift surveys up to z <~ 0.8 with galaxies and z ~ 2 with Ly-$\alpha$ forest, providing precise distance measurements and $H_0$ with < 2% uncertainty in flat $\Lambda$CDM. Future BAO surveys will probe the distance scale with percent-level precision. HI intensity mapping has great potential to map BAO distances at z ~ 0.8 and beyond with precisions of a few percent. The next years ahead will be exciting as various cosmological probes reach 1% uncertainty in determining $H_0$, to assess the current tension in $H_0$ measurements that could indicate new physics.Comment: Review article accepted for publication in Space Science Reviews (Springer), 45 pages, 10 figures. Chapter of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Ag

Impurity and interface bound states in dx2−y2+idxyd_{x^2-y^2}+id_{xy} and px+ipyp_x+ip_y superconductors

Motivated by recent discoveries of novel superconductors such as Na$_x$CoO$_2\cdot y$H$_2$O and Sr$_2$RuO$_4$, we analysize features of quasi-particle scattering due to impurities and interfaces for possible gapful $d_{x^2-y^2}+id_{xy}$ and $p_x+ip_y$ Cooper pairing. A bound state appears near a local impurity, and a band of bound states form near an interface. We obtained analytically the bound state energy, and calculated the space and energy dependent local density of states resolvable by high-resolution scanning tunnelling microscopy. For comparison we also sketch results of impurity and surface states if the pairing is nodal p- or d-wave.Comment: 4 pages, 4 figure

Cosmological Implications of Neutrinos

The lectures describe several cosmological effects produced by neutrinos. Upper and lower cosmological limits on neutrino mass are derived. The role that neutrinos may play in formation of large scale structure of the universe is described and neutrino mass limits are presented. Effects of neutrinos on cosmological background radiation and on big bang nucleosynthesis are discussed. Limits on the number of neutrino flavors and mass/mixing are given.Comment: 41 page, 7 figures; lectures presented at ITEP Winter School, February, 2002; to be published in the Proceeding