Combinatorial persistency criteria for multicut and max-cut

In combinatorial optimization, partial variable assignments are called persistent if they agree with some optimal solution. We propose persistency criteria for the multicut and max-cut problem as well as fast combinatorial routines to verify them. The criteria that we derive are based on mappings that improve feasible multicuts, respectively cuts. Our elementary criteria can be checked enumeratively. The more advanced ones rely on fast algorithms for upper and lower bounds for the respective cut problems and max-flow techniques for auxiliary min-cut problems. Our methods can be used as a preprocessing technique for reducing problem sizes or for computing partial optimality guarantees for solutions output by heuristic solvers. We show the efficacy of our methods on instances of both problems from computer vision, biomedical image analysis and statistical physics

Structure of Six-Dimensional Microstate Geometries

We investigate the structure of smooth and horizonless microstate geometries in six dimensions, in the spirit of the five-dimensional analysis of Gibbons and Warner [arXiv:1305.0957]. In six dimensions, which is the natural setting for horizonless geometries with the charges of the D1-D5-P black hole, the natural black objects are strings and there are no Chern-Simons terms for the tensor gauge fields. However, we still find that the same reasoning applies: in absence of horizons, there can be no smooth stationary solutions without non-trivial topology. We use topological arguments to describe the Smarr formula in various examples: the uplift of the five-dimensional minimal supergravity microstates to six dimensions, the two-charge D1-D5 microstates, and the non-extremal JMaRT solution. We also discuss D1-D5-P superstrata and confirm that the Smarr formula gives the same result as for the D1-D5 supertubes which are topologically equivalent.Comment: 29 pages, v2: references added, published versio

Single-Cell Impedance Spectroscopy

Impedance spectroscopy (IS) is an important tool for cell detection and characterization in medical and food safety applications. In this thesis, the Cal Poly Biofluidics Lab’s impedance spectroscopy system was re-evaluated and optimized for single-cell impedance spectroscopy. To evaluate the IS system, an impedance spectroscopy bioMEMS chip was fabricated in the Cal Poly Microfabcrication lab, software was developed to run IS experiments, and studies were run to validate the system. To explore IS optimization, Maxwell’s mixture theorem and the Schwartz-Christoffel transform were used to calculate an analytic impedance solution to the co-planar electrode system,a novel volume fraction to account for the non-uniformity of the electric field was developed to increase the accuracy of the analytic solution and to investigate the effect of cell position on the impedance spectrum, a software program was created to allow easy access to the analytic solution, and FEA models were developed to compare to the analytic solution and to investigate the effect of complex device geometry

Experimental study of the phase transition in KD2PO4

he ferroelectric phase transition in KD2PO4has been studied using coherent neutron inelastic scattering. The low frequency phonon dispersion relations were determined in the two principal symmetry directions. The results were fitted to a central force rigid ion model which gave good agreement with the acoustic branches and fee lowest frequency optic branches. Group theory was used to simplify all calculations. None of the phonon modes was temperature dependent and therefore the ferroelectric transition was not caused by a soft mode. Quasi-elastic critical scattering was observed, the intensity of which increased as fee transition temperature was approached. The scattering extended throughout each lirillouin zone and was peaked at reciprocal lattice points. The variation of fee intensity in the scattering plane showed that fee displacements of the atoms in the ferroelectric fluctuations were similar to those relating fee paraelectric and ferroelectric phases. The distribution of the intensity around each reciprocal lattice point showed the effect of the macroscopic field associated wife the ferroelectric fluctuations. A simple Ising model wife next nearest neighbour and Coulomb interactions described fee results well. A microscopic model for KDP type crystals is proposed. The model neglects sail dynamic effects, describes the experimental results and shows that the interaction of the phonons with the ferroelectric fluctuations is of more importance than previously thought. The model also predicts the shape of ferroelectric critical scattering to other ferroelectric and antiferroelectric KDP type crystals

Generalised Umbral Moonshine

Umbral moonshine describes an unexpected relation between 23 finite groups arising from lattice symmetries and special mock modular forms. It includes the Mathieu moonshine as a special case and can itself be viewed as an example of the more general moonshine phenomenon which connects finite groups and distinguished modular objects. In this paper we introduce the notion of generalised umbral moonshine, which includes the generalised Mathieu moonshine [Gaberdiel M.R., Persson D., Ronellenfitsch H., Volpato R., Commun. Number Theory Phys. 7 (2013), 145-223] as a special case, and provide supporting data for it. A central role is played by the deformed Drinfel'd (or quantum) double of each umbral finite group $G$, specified by a cohomology class in $H^3(G,U(1))$. We conjecture that in each of the 23 cases there exists a rule to assign an infinite-dimensional module for the deformed Drinfel'd double of the umbral finite group underlying the mock modular forms of umbral moonshine and generalised umbral moonshine. We also discuss the possible origin of the generalised umbral moonshine

Variability in coal prices: evidence from the U.S.

Monthly U.S. coal price time series data are tested to determine the persistence of shocks. The time series is then disaggregated by length of agreement to further explore the first and second moments of pricing behaviour. Results show that prices have a variance that changes over time and tend to be highly persistent. Prices from long-term transaction agreements tend to require more lags and have a higher degree of persistence

Accounting education at a crossroad in 2010 and challenges facing accounting education in Australia

Of the various reports released in 2010, two purport to examine the state of accounting education in Australia. These are Accounting Education at a Crossroad in 2010 and Challenges Facing Accounting Education in Australia. Both were released as collaborations of the leading academic organisation, the Accounting and Finance Association of Australia and New Zealand (AFAANZ) or professional accounting bodies in Australia including the Institute of Chartered Accountants in Australia (ICAA), the Institute of Public Accountants (IPA),1 and Certified Practising Accountants of Australia (CPA Australia). As their titles imply, the main thrust of these reports is to examine the challenges facing accounting education in Australian universities and, as such, they act as the input for this AE Briefing. The main challenges articulated in these reports portray a sector suffering from the combined pressure of a large international student enrolment, high student-to-staff ratios, an inadequate funding model, and an ageing academic staff profile. By way of commentary, we suggest that, if these gloomy circumstances continue to develop unabated, then the future for the sector will play out as a &lsquo;perfect storm&rsquo;2 with the sector suffering on-going troubled development.<br /