Film study for a star correlator Final report

Photographic recording film evaluation for star field image processing in spacecraft environment and use in star correlato

Momentum transfer dependence of the proton's electric and magnetic polarizabilities

The Q^2-dependence of the sum of the electric and magnetic polarizabilities of the proton is calculated over the range 0 \leq Q^2 \leq 6 GeV^2 using the generalized Baldin sum rule. Employing a parametrization of the F_1 structure function valid down to Q^2 = 0.06 GeV^2, the polarizabilities at the real photon point are found by extrapolating the results of finite Q^2 to Q^2 = 0 GeV^2. We determine the evolution over four-momentum transfer to be consistent with the Baldin sum rule using photoproduction data, obtaining \alpha + \beta = 13.7 \pm 0.7 \times 10^{-4}\, \text{fm}^3.Comment: 4 pages, 3 figure

Baryon resonances and hadronic interactions in a finite volume

In a finite volume, resonances and multi-hadron states are identified by discrete energy levels. When comparing the results of lattice QCD calculations to scattering experiments, it is important to have a way of associating the energy spectrum of the finite-volume lattice with the asymptotic behaviour of the S-matrix. A new technique for comparing energy eigenvalues with scattering phase shifts is introduced, which involves the construction of an exactly solvable matrix Hamiltonian model. The model framework is applied to the case of $\Delta\rightarrow N\pi$ decay, but is easily generalized to include multi-channel scattering. Extracting resonance parameters involves matching the energy spectrum of the model to that of a lattice QCD calculation. The resulting fit parameters are then used to generate phase shifts. Using a sample set of pseudodata, it is found that the extraction of the resonance position is stable with respect to volume for a variety of regularization schemes, and compares favorably with the well-known Luescher method. The model-dependence of the result is briefly investigated.Comment: 7 pages, 3 figures. Talk presented at the 30th International Symposium on Lattice Field Theory (Lattice 2012), June 24-29, 2012, Cairns, Australi

On topological phases of spin chains

Symmetry protected topological phases of one-dimensional spin systems have been classified using group cohomology. In this paper, we revisit this problem for general spin chains which are invariant under a continuous on-site symmetry group G. We evaluate the relevant cohomology groups and find that the topological phases are in one-to-one correspondence with the elements of the fundamental group of G if G is compact, simple and connected and if no additional symmetries are imposed. For spin chains with symmetry PSU(N)=SU(N)/Z_N our analysis implies the existence of N distinct topological phases. For symmetry groups of orthogonal, symplectic or exceptional type we find up to four different phases. Our work suggests a natural generalization of Haldane's conjecture beyond SU(2).Comment: 18 pages, 7 figures, 2 tables. Version v2 corresponds to the published version. It includes minor revisions, additional references and an application to cold atom system

Quark-hadron duality constraints on \gamma Z box corrections to parity-violating elastic scattering

We examine the interference \gamma Z box corrections to parity-violating elastic electron--proton scattering in the light of the recent observation of quark-hadron duality in parity-violating deep-inelastic scattering from the deuteron, and the approximate isospin independence of duality in the electromagnetic nucleon structure functions down to Q^2 \approx 1 GeV^2. Assuming that a similar behavior also holds for the \gamma Z proton structure functions, we find that duality constrains the \gamma Z box correction to the proton's weak charge to be \Re e\, \square_{\gamma Z}^V = (5.4 \pm 0.4) \times 10^{-3} at the kinematics of the Q_{\text{weak}} experiment. Within the same model we also provide estimates of the \gamma Z corrections for future parity-violating experiments, such as MOLLER at Jefferson Lab and MESA at Mainz.Comment: 10 pages, 3 figures. Final version to be published in Phys. Lett.

Resilience and Community in the Age of World-System Collapse

In this essay we explore how humans might face systemic collapse and/or entry into a dark age through forms of community resilience. We also note that nature, types of communities, and degrees of resilience differ in core, peripheral, and semiperipheral areas of the contemporary world-system. Core or global north or first world communities have all but disintegrated due to neoliberal policies. However, communities in peripheral and semiperipheral areas are more emergent, and more resilient. These areas are most likely to have or to creatively develop strategies to overcome global collapse. We further argue that social scientists need to develop new definitions of community that go beyond contemporary conceptualizations

The principle of equivalence and projective structure in space-times

This paper discusses the extent to which one can determine the space-time metric from a knowledge of a certain subset of the (unparametrised) geodesics of its Levi-Civita connection, that is, from the experimental evidence of the equivalence principle. It is shown that, if the space-time concerned is known to be vacuum, then the Levi-Civita connection is uniquely determined and its associated metric is uniquely determined up to a choice of units of measurement, by the specification of these geodesics. It is further demonstrated that if two space-times share the same unparametrised geodesics and only one is assumed vacuum then their Levi-Civita connections are again equal (and so the other metric is also a vacuum metric) and the first result above is recovered.Comment: 23 pages, submitted to Classical and Quantum Gravit

Do jumbo-CD holders care about anything?

Uninsured deposits represent a theoretically appealing but relatively untested alternative to subordinated debt for incorporating market discipline into banking supervision. To make the deposit market a useful supervisory tool, it is necessary to know what types of risk are priced by depositors and in what proportions. Using a clustering technique to select from among a large set of potential regressors, as well as a carefully chosen set of control variables, we attempt to determine the types of risk that cause uninsured depositors to react in both the price and quantity dimensions. As a benchmark for economic significance, we estimate similar regressions on supervisory ratings. We find that, in contrast to government supervisors, depositors have not priced most types of risk since 1997. Indeed, the only risk variables that consistently come up as statistically significant are those that measure capital adequacy. Our interpretation of these results is that, because aggregate banking conditions are good, it is not worth depositors' effort to investigate individual bank quality very carefully. We conclude that, in the current economic and regulatory environment, the market is content to delegate most of its monitoring and discipline to the government. To the extent that it does monitor, it only monitors capital. The jumbo-CD market is thus not likely to be of much supervisory use, particularly given that examiners already have good information about capital levels. The depositor emphasis on capital also supports the conjecture that market discipline was responsible for much of the recent capital build-up.Bank deposits ; Bank supervision

Efficient Implementation of Elastohydrodynamics via Integral Operators

The dynamics of geometrically non-linear flexible filaments play an important role in a host of biological processes, from flagella-driven cell transport to the polymeric structure of complex fluids. Such problems have historically been computationally expensive due to numerical stiffness associated with the inextensibility constraint, as well as the often non-trivial boundary conditions on the governing high-order PDEs. Formulating the problem for the evolving shape of a filament via an integral equation in the tangent angle has recently been found to greatly alleviate this numerical stiffness. The contribution of the present manuscript is to enable the simulation of non-local interactions of multiple filaments in a computationally efficient manner using the method of regularized stokeslets within this framework. The proposed method is benchmarked against a non-local bead and link model, and recent code utilizing a local drag velocity law. Systems of multiple filaments (1) in a background fluid flow, (2) under a constant body force, and (3) undergoing active self-motility are modeled efficiently. Buckling instabilities are analyzed by examining the evolving filament curvature, as well as by coarse-graining the body frame tangent angles using a Chebyshev approximation for various choices of the relevant non-dimensional parameters. From these experiments, insight is gained into how filament-filament interactions can promote buckling, and further reveal the complex fluid dynamics resulting from arrays of these interacting fibers. By examining active moment-driven filaments, we investigate the speed of worm- and sperm-like swimmers for different governing parameters. The MATLAB(R) implementation is made available as an open-source library, enabling flexible extension for alternate discretizations and different surrounding flows.Comment: 37 pages, 17 figure