Gaussian fields and Gaussian sheets with generalized Cauchy covariance structure

Two types of Gaussian processes, namely the Gaussian field with generalized Cauchy covariance (GFGCC) and the Gaussian sheet with generalized Cauchy covariance (GSGCC) are considered. Some of the basic properties and the asymptotic properties of the spectral densities of these random fields are studied. The associated self-similar random fields obtained by applying the Lamperti transformation to GFGCC and GSGCC are studied.Comment: 32 pages, 6 figure

Relativistic linear stability equations for the nonlinear Dirac equation in Bose-Einstein condensates

We present relativistic linear stability equations (RLSE) for quasi-relativistic cold atoms in a honeycomb optical lattice. These equations are derived from first principles and provide a method for computing stabilities of arbitrary localized solutions of the nonlinear Dirac equation (NLDE), a relativistic generalization of the nonlinear Schr\"odinger equation. We present a variety of such localized solutions: skyrmions, solitons, vortices, and half-quantum vortices, and study their stabilities via the RLSE. When applied to a uniform background, our calculations reveal an experimentally observable effect in the form of Cherenkov radiation. Remarkably, the Berry phase from the bipartite structure of the honeycomb lattice induces a boson-fermion transmutation in the quasi-particle operator statistics.Comment: 6 pages, 3 figure

A scheme for symmetrization verification

We propose a scheme for symmetrization verification in two-particle systems, based on one-particle detection and state determination. In contrast to previous proposals, it does not follow a Hong-Ou-Mandel-type approach. Moreover, the technique can be used to generate superposition states of single particles

A Multi-Factor Analysis of AREIT Returns

Since 1990, the Australian Real Estate Investment Trust (AREIT) sector has experienced substantial growth and popularity. While the AREIT sector had benefit from the increased flow of funds from institutional investors during the 1997 Asian financial crisis, the recent impact of the 2008 global financial crisis has been a negative one. In this paper, we examine the sensitivities of annualised AREIT returns against a set of seven firm-specific variables and four market-wide risk variables. Balanced and unbalanced panel regressions are conducted on three sub-periods during 1990 - 2008 corresponding to the major phases in evolution of the AREIT sector. Our regression results find that size has a negative impact on returns, and this effect has been diminishing over time. Overall market risk was also found to be significant and positive only since 2003, suggesting that recently AREITs behave more like stocks and less like defensive assets. The relationship with exchange rate risk has been positive in recent years, due to more AREITs choosing to diversify internationally, particularly in the U.S. property markets. Our findings on the relationship between market-to-book ratios and AREIT returns depart from standard finance literature. In comparison to REITs in other countries, AREITs have shifted their preferences away from property-type diversification and into more specialised investment strategies. We also find contrasting evidence on the impact of international diversification, and that domestic AREITs provide better returns than internationally diversified counterparts. The relationship between returns and short term interest rates was found to be positive and significant prior to 2002, and the relationship with long-term interest rates was found to be negative and significant since 2003, suggesting that AREITs exhibit less bond-like characteristics in the past five years.AREITs, AREIT returns, Property-type diversification, International diversification, Panel regressions

Discovery of Radio Emission from the Tight M8 Binary: LP 349-25

We present radio observations of 8 ultracool dwarfs with a narrow spectral type range (M8-M9.5) using the Very Large Array at 8.5 GHz. Only the tight M8 binary LP 349-25 was detected. LP 349-25 is the tenth ultracool dwarf system detected in radio and its trigonometric parallax pi = 67.6 mas, recently measured by Gatewood et al., makes it the furthest ultracool system detected by the Very Large Array to date, and the most radio-luminous outside of obvious flaring activity or variability. With a separation of only 1.8 AU, masses of the components of LP 349-25 can be measured precisely without any theoretical assumptions (Forveille et al.), allowing us to clarify their fully-convective status and hence the kind of magnetic dynamo in these components which may play an important role to explain our detection of radio emission from these objects. This also makes LP 349-25 an excellent target for further studies with better constraints on the correlations between X-ray, radio emission and stellar parameters such as mass, age, temperature, and luminosity in ultracool dwarfs.Comment: accepted by ApJ, referee's comments included, typo in equation 1 correcte

Modeling Single-File Diffusion by Step Fractional Brownian Motion and Generalized Fractional Langevin Equation

Single-file diffusion behaves as normal diffusion at small time and as anomalous subdiffusion at large time. These properties can be described by fractional Brownian motion with variable Hurst exponent or multifractional Brownian motion. We introduce a new stochastic process called Riemann-Liouville step fractional Brownian motion which can be regarded as a special case of multifractional Brownian motion with step function type of Hurst exponent tailored for single-file diffusion. Such a step fractional Brownian motion can be obtained as solution of fractional Langevin equation with zero damping. Various types of fractional Langevin equations and their generalizations are then considered to decide whether their solutions provide the correct description of the long and short time behaviors of single-file diffusion. The cases where dissipative memory kernel is a Dirac delta function, a power-law function, and a combination of both of these functions, are studied in detail. In addition to the case where the short time behavior of single-file diffusion behaves as normal diffusion, we also consider the possibility of the process that begins as ballistic motion.Comment: 12 pages, 7 figure

Reversibility of Red blood Cell deformation

The ability of cells to undergo reversible shape changes is often crucial to their survival. For Red Blood Cells (RBCs), irreversible alteration of the cell shape and flexibility often causes anemia. Here we show theoretically that RBCs may react irreversibly to mechanical perturbations because of tensile stress in their cytoskeleton. The transient polymerization of protein fibers inside the cell seen in sickle cell anemia or a transient external force can trigger the formation of a cytoskeleton-free membrane protrusion of micrometer dimensions. The complex relaxation kinetics of the cell shape is shown to be responsible for selecting the final state once the perturbation is removed, thereby controlling the reversibility of the deformation. In some case, tubular protrusion are expected to relax via a peculiar "pearling instability".Comment: 4 pages, 3 figure