Quantum Hyperplane Section Theorem For Homogeneous Spaces

We formulated a mirror-free approach to the mirror conjecture, namely, quantum hyperplane section conjecture, and proved it in the case of nonnegative complete intersections in homogeneous manifolds. For the proof we followed the scheme of Givental's proof of a mirror theorem for toric complete intersections.Comment: 24 pages, LaTeX 2e. The presentation is improved a lo

X-ray Variability and Evidence for Pulsations from the Unique Radio Pulsar/X-ray Binary Transition Object FIRST J102347.6+003841

We report on observations of the unusual neutron-star binary system FIRST J102347.6+003841 carried out using the XMM-Newton satellite. This system consists of a radio millisecond pulsar in an 0.198-day orbit with a ~0.2 solar-mass Roche-lobe-filling companion, and appears to have had an accretion disk in 2001. We observe a hard power-law spectrum (\Gamma = 1.26(4)) with a possible thermal component, and orbital variability in X-ray flux and possibly hardness of the X-rays. We also detect probable pulsations at the pulsar period (single-trial significance ~4.5 sigma from an 11(2)% modulation), which would make this the first system in which both orbital and rotational X-ray pulsations are detected. We interpret the emission as a combination of X-rays from the pulsar itself and from a shock where material overflowing the companion meets the pulsar wind. The similarity of this X-ray emission to that seen from other millisecond pulsar binary systems, in particular 47 Tuc W (PSR J0024-7204W) and PSR J1740-5340, suggests that they may also undergo disk episodes similar to that seen in J1023 in 2001.Comment: 14 pages, 5 figures, 1 table; accepted to Ap

Comovement in UK real estate sector returns

Engle et al. (1990) distinguish between 'heat waves' and 'meteor showers' in an analogy which tries to differentiate between particular effects, not transmitted among markets, and general effects, which tend to affect all the markets, although different markets can be affected to different degrees. This paper applies this approach to the study of the monthly returns of four real estate market sectors: Office, Retail, Industrial and Retail Warehouses in the UK over the period 1979:2 to 1997:12. A VAR methodology used with the aim of detecting the causal relations and dynamic interactions among sector returns, as well as the transmission mechanisms of their information flows. The results obtained permit us to conclude that there is a good deal of integration between the monthly return time series for all the sectors. Therefore, diversification across real estate market sectors does not allow for the reduction of risk without sacrificing expected returns

Asymptotic expansion of the difference of two Mahler measures

We show that for almost every polynomial P(x,y) with complex coefficients, the difference of the logarithmic Mahler measures of P(x,y) and P(x,x^n) can be expanded in a type of formal series similar to an asymptotic power series expansion in powers of 1/n. This generalizes a result of Boyd. We also show that such an expansion is unique and provide a formula for its coefficients. When P has algebraic coefficients, the coefficients in the expansion are linear combinations of polylogarithms of algebraic numbers, with algebraic coefficients.Comment: 25 pages. V2: Demoted previous Corollary 1 to a comment, after realizing that Boyd had already proved that bit. Made small corrections to Lemma 5, streamlined the proof of Lemma 9, and reworded section 9.

Bulk Emission of Scalars by a Rotating Black Hole

We study in detail the scalar-field Hawking radiation emitted into the bulk by a higher-dimensional, rotating black hole. We numerically compute the angular eigenvalues, and solve the radial equation of motion in order to find transmission factors. The latter are found to be enhanced by the angular momentum of the black hole, and to exhibit the well-known effect of superradiance. The corresponding power spectra for scalar fields show an enhancement with the number of dimensions, as in the non-rotating case. On the other hand, the proportion of the total (i.e., bulk+brane) power that is emitted into the bulk decreases monotonically with the angular momentum. We compute the total mass loss rate of the black hole for a variety of black-hole angular momenta and bulk dimensions, and find that, in all cases, the bulk emission remains significantly smaller than the brane emission. The angular-momentum loss rate is also computed and found to have a smaller value in the bulk than on the brane