Random Walks and Market Efficiency: Evidence from International Real Estate Markets

This study performs tests of the random walk hypothesis for international commercial real estate markets utilizing stock market indices of real estate share prices for three geographical regions: Europe, Asia and North America. The augmented Dickey-Fuller and Phillips-Perron unit root tests and Cochrane variance ratio test find that each of these markets (as well as associated broader stock markets) exhibits random walk behavior. Moreover, a non-parametric runs test provides support for weak-form market efficiency in the real estate markets. In addition, Johansen-Juselius co-integration analysis reveals that all three markets appear co-integrated and share a common long-run stochastic trend. Results of co-integration analyses and vector error correction models suggest that diversification benefits through international real estate securities can only be achieved in the short run.

The cone of pseudo-effective divisors of log varieties after Batyrev

In these notes we investigate the cone of nef curves of projective varieties, which is the dual cone to the cone of pseudo-effective divisors. We prove a structure theorem for the cone of nef curves of projective $\mathbb Q$-factorial klt pairs of arbitrary dimension from the point of view of the Minimal Model Program. This is a generalization of Batyrev's structure theorem for the cone of nef curves of projective terminal threefolds.Comment: 15 pages. v2: Completely rewritten paper. Structure theorem for the cone of nef curves proved in arbitrary dimension using results of Birkar, Cascini, Hacon and McKernan. To appear in Mathematische Zeitschrif

Theory of Neutron Diffraction from the Vortex Lattice in UPt3

Neutron scattering experiments have recently been performed in the superconducting state of UPt3 to determine the structure of the vortex lattice. The data show anomalous field dependence of the aspect ratio of the unit cell in the B phase. There is apparently also a change in the effective coherence length on the transition from the B to the C phases. Such observations are not consistent with conventional superconductvity. A theory of these results is constructed based on a picture of two-component superconductivity for UPt3. In this way, these unusual observations can be understood. There is a possible discrepancy between theory and experiment in the detailed field dependence of the aspect ratio.Comment: 11 pages; uses REVTEX, APS and PRABIB styles; 2 Postscript figure files include

Strong Lefschetz elements of the coinvariant rings of finite Coxeter groups

For the coinvariant rings of finite Coxeter groups of types other than H$_4$, we show that a homogeneous element of degree one is a strong Lefschetz element if and only if it is not fixed by any reflections. We also give the necessary and sufficient condition for strong Lefschetz elements in the invariant subrings of the coinvariant rings of Weyl groups.Comment: 18 page

Lucky or clever? From expectations to responsibility judgments

How do people hold others responsible for the consequences of their actions? We propose a computational model that attributes responsibility as a function of what the observed action reveals about the person, and the causal role that the person's action played in bringing about the outcome. The model first infers what type of person someone is from having observed their action. It then compares a prior expectation of how a person would behave with a posterior expectation after having observed the person's action. The model predicts that a person is blamed for negative outcomes to the extent that the posterior expectation is lower than the prior, and credited for positive outcomes if the posterior is greater than the prior. We model the causal role of a person's action by using a counterfactual model that considers how close the action was to having been pivotal for the outcome. The model captures participants' responsibility judgments to a high degree of quantitative accuracy across three experiments that cover a range of different situations. It also solves an existing puzzle in the literature on the relationship between action expectations and responsibility judgments. Whether an unexpected action yields more or less credit depends on whether the action was diagnostic for good or bad future performance

Stress balance in nano-patterned N/Cu(001) surfaces

We employ helium atom scattering (HAS) and density functional theory (DFT) based on the ultrasoft pseudopotential scheme and the plane-wave basis set to investigate the strain and stress balance in nano-patterned N/Cu(001) surfaces. HAS shows that, with increasing N coverage (and decreasing stripe widths), the stress-relief-driven lateral expansion of the averaged lattice parameter within finite-sized N-containing patches reduces from 3.5% to 1.8% and that, beyond a critical exposure, the lateral expansion of the patches increases again slightly, to 2.4%. The latter implies that in this higher coverage range the compressive stress is partially relieved via another mechanism, which turns out to be nucleation of Cu-vacancy trenches. In full agreement with the above and previous experimental observations, DFT calculations show that an optimized N-induced c(2\times2) structure has a net surface stress level of 4.2 N/m and such stress is effectively relieved when stripes of clean Cu(001) form along the direction or when trench-like steps of Cu atoms form along the direction. Additionally, the calculations demonstrate that (contrary to earlier suggestions) rumpling displacements within the outermost Cu layer do not act to relieve the compressive surface stress levels and that, while clock-like displacements could relieve stress levels, such displacements are energetically unstable

Integral Grothendieck-Riemann-Roch theorem

We show that, in characteristic zero, the obvious integral version of the Grothendieck-Riemann-Roch formula obtained by clearing the denominators of the Todd and Chern characters is true (without having to divide the Chow groups by their torsion subgroups). The proof introduces an alternative to Grothendieck's strategy: we use resolution of singularities and the weak factorization theorem for birational maps.Comment: 24 page

Mechanism of thermally activated c-axis dissipation in layered High-Tc_c superconductors at high fields

We propose a simple model which explains experimental behavior of $c$-axis resistivity in layered High-T$_c$ superconductors at high fields in a limited temperature range. It is generally accepted that the in-plane dissipation at low temperatures is caused by small concentration of mobile pancake vortices whose diffusive motion is thermally activated. We demonstrate that in such situation a finite conductivity appears also in $c$-direction due to the phase slips between the planes caused by the mobile pancakes. The model gives universal relation between the components of conductivity which is in good agreement with experimental data.Comment: RevTeX, 4 pages, 2 Postscript figure

The Canonical Model of a Singular Curve

We give refined statements and modern proofs of Rosenlicht's results about the canonical model C' of an arbitrary complete integral curve C. Notably, we prove that C and C' are birationally equivalent if and only if C is nonhyperelliptic, and that, if C is nonhyperelliptic, then C' is equal to the blowup of C with respect to the canonical sheaf \omega. We also prove some new results: we determine just when C' is rational normal, arithmetically normal, projectively normal, and linearly normal.Comment: 28 pages, no figures, IV Congresso Iberoamericano de Geometria Complex

Moduli of mathematical instanton vector bundles with odd c_2 on projective space

The problem of irreducibility of the moduli space I_n of rank-2 mathematical instanton vector bundles with arbitrary positive second Chern class n on the projective 3-space is considered. The irreducibility of I_n was known for small values of n: Barth 1977 (n=1), Hartshorne 1978 (n=2), Ellingsrud and Stromme 1981 (n=3), Barth 1981 (n=4), Coanda, Tikhomirov and Trautmann 2003 (n=5). In this paper we prove the irreducibility of I_n for an arbitrary odd n.Comment: 62 page