We show how 3-dimensional, N=2 supersymmetric theories, including super QCD with matter fields, can be put on the lattice with existing techniques, in a way which will recover supersymmetry in the small lattice spacing limit, with O(a) lattice spacing suppressed SUSY breaking effects.

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2008. / Title from PDF t.p. (viewed on Jul 29, 2009). Source: Dissertation Abstracts International, Volume: 69-12, Section: B, page: 7583. Adviser: Charles J. Horowitz.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6821. Adviser: Todd J. Martinez. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6483. Adviser: Scott S. Willenbrock. Includes bibliographical references (leaves 80-82) Available on microfilm from Pro Quest Information and Learning.

A model organism Caenorhabditis elegans is a free-living nematode that feeds on bacteria in the wild. To survive, it has to be able to distinguish between benign and pathogenic microorganisms. Thanks to its simple neural system it is capable of determining whether the source of food is dangerous and physically avoid it. In this work we present evidence that this avoidance behavior depends on the nematode population density. The worms exposed to a pathogen secrete an alarm pheromone, which drives the population away from the danger. Worms carrying a mutation in the acox-1 gene (involved in the pheromone biosynthesis) are unable to produce the alarm signal and odr-7 mutants fail to react to it suggesting that AWA neurons are involved in the pheromone detection. We developed a simple phenomenological model that quantifies the effects of the secreted pheromone and was able to reproduce major features of the nematodes' behavior at the population level. We show that the collective avoidance is not restricted to C. elegans as other Rhabditida nematodes also exhibit this behavior. Furthermore, the alarm signal left by C. elegans in the bacterial lawn is detected by most of the other species tested but some of them were attracted to it rather than repulsed which suggests that the chemical signal is not conserved between them.

Since its introduction one decade ago, the quantum algorithm for chemistry has been among the most anticipated applications of quantum computers. However, as the age of industrial quantum technology dawns, so has the realization that even “polynomial” resource overheads are often prohibitive. There remains a large gap between the capabilities of existing hardware and the resources required to quantum compute classically intractable problems in chemistry. The primary contribution of this dissertation is to take meaningful steps towards reducing the costs of three approaches to quantum computing chemistry. First, we discuss how chemistry problems can be embedded in Hamiltonians suitable for commercially manufactured quantum annealing machines. We introduce schemes for more efficiently compiling problems to annealing Hamiltonians and apply the techniques to problems in protein folding, gene expression, and cheminformatics. Second, we introduce the first adiabatic quantum algorithm for fermionic simulation. Towards this end, we develop tools which embed arbitrary universal Hamiltonians in constrained hardware at a reduced cost. Finally, we turn our attention to the digital quantum algorithm for chemistry. By exploiting the locality of physical interactions, we quadratically reduce the number of terms which must be simulated. By analyzing the scaling of time discretization errors in terms of chemical properties, we obtain significantly tighter bounds on the minimum number of time steps which must be simulated. Also included in this dissertation is a protocol for preparing configuration interaction states that is asymptotically superior to all prior results and the details of the most accurate experimental quantum simulation of chemistry ever performed. / Chemical Physics

Accurate treatment of the long-range electron correlation energy, including dispersion interactions, is essential for describing the structure, dynamics, and function of a wide variety of systems. Among the most accurate models for including dispersion into density functional theory (DFT) is the range-separated many-body dispersion (MBD) method [A. Ambrosetti et al., J. Chem. Phys. 2014, 140, 18A508], in which the long-range correlation energy is computed from a model system of coupled quantum harmonic oscillators. In this work, we seek to extend the applicability of the MBD model by developing the analytical gradients necessary to compute MBD corrections to ionic forces, unit-cell stresses, phonon modes, and self-consistent updates to the Kohn-Sham potential. We include all implicit coordinate dependencies arising from charge density partitioning, as we find that neglecting these terms leads to unacceptably large relative errors in the MBD forces. Such errors would impact the predictive nature of ab initio molecular dynamics simulations employing MBD. We develop a new efficient implementation of the MBD correlation energy and forces within the Quantum ESPRESSO software package and rigorously test its numerical stability and convergence properties for condensed phase simulations. Additionally, we re-parameterize the MBD model for use with a wide variety of generalized gradient approximation exchange-correlation functionals. We demonstrate the efficiency and accuracy of these MBD gradient corrections for optimizations of isolated dispersively bound molecular systems, as well as representative condensed phase systems including adsorbed hydrocarbons, layered materials, and hydrogen-bonded crystals. Where highly accurate reference geometries are available, we find the DFT+MBD method significantly improves the predicted structures of these systems and consistently outperforms popular pairwise-additive DFT-D dispersion corrections. Though significant work remains in the benchmarking and testing of these contributions to the MBD model, we are optimistic that these methodological developments will enable many exciting discoveries of beyond-pairwise dispersive effects in organic materials. / Physics

In this thesis, we study collective phenomena that arise from microscopic fluctuations at the individual level of two different living populations. First, we study evolutionary dynamics of two-species competitions in a well-mixed environment subject to population size fluctuations. We demonstrate a mechanism for neutral evolution such that population size fluctuations favor a fixation of one species over the other. An effective evolutionary dynamics for fluctuation-induced selection is derived. We then investigate strong mutualism, in a limit where a varying population size can strongly influence the evolutionary dynamics. We determine fixation probabilities as well as mean fixation times taking into account the population size degree of freedom. The results elucidate the interplay between population size fluctuations and evolutionary dynamics in well-mixed systems. Second, we investigate  single species marine population  subject to a constant flow field and quenched random spatially fluctuating growth rates.  We show that the non-equilibrium steady-state population density of a generalized Fisher-Kolmogorov-Petrovsky-Piscounov (FKPP) equation develops a flow-driven striation pattern.  The striations are highly asymmetric with a longitudinal correlation length that diverges linearly with the flow speed and a transverse correlation length that approaches a finite velocity-independent value. The findings suggest that, although the growth disorder can be spatially uncorrelated, correlated population structures with striations emerge naturally at sufficiently strong advection. / Physics

No description available.

On étude les effets non-perturbatifs généré par des branes instantoniques Euclidiens en compactifications de la théorie des cordes de type I/II avec orientifolds et D-branes magnétisées. Le focus est sur les instantons qui peuvent générer des corrections au superpotentiel. Une condition nécessaire est que les instantons doivent enrouler des cycles rigides. On considère la compactification de la théorie de Type I (IIB) sur l'orientifold T^6/Z_2xZ_2 avec torsion discrète et D-branes magnétisées. Les instantons enroulant le même cycle que l'O-plane exotique (requis par la torsion discrète) ont la structure désiré de modes zéro pour générer des corrections au superpotentiel. On construit des modèles globales basée sur cet orientifold ou les instantons génère des termes linaires et de termes de masse dans le superpotentiel. En théorie des cordes on calcule un couplage physique duquel on doit extraire la partie olomorphique pour obtenir le superpotentiel non-perturbatif. Les facteurs non-olomorphiques sont absorbés dans le potentiel de Kähler et dans redéfinitions des champs chiraux et modules des cordes fermées. On a dérivé ces redéfinitions pour les compactifications toroïdales (avec orientifolds) de la théorie de Type I avec branes magnétisées et lignes Wilson. Finalement, on a considéré des modèles globales avec des termes linéaires. On a calculé explicitement le superpotentiel non-perturbatif pour les orientifolds toroïdales. On a montré comment faire la somme sur les contributions a un instanton. Les modèles analysées possédaient des vides non-perturbatifs supersymétriques ou le group de jauge était brisé et certains modules des cordes ouvertes étaient stabilisés.