Rebuilding Mathematics on a Quantum Logical Foundation
Richard deJonghe University of Illinois at Chicago
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Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice
Gang Chen Fudan University
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Calculating the free energy of antimicrobial peptide (HHC-36) dimerization in bulk
shaqa vafa University of Guelph
PIRSA:13120043 -
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Budding transition of a self-avoiding polymer confined by a soft membrane adhering onto a flat wall
Yu-Cheng Su University of Waterloo
PIRSA:13120041 -
Dynamical simulation of disordered micelles in a diblock copolymer melt with fluctuations
Russell Spencer University of Guelph
PIRSA:13120040 -
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Phase-field model for cellular monolayers : a cancer cell migration studyauthors : Benoit Palmieri and Martin Grant
Benoit Palmieri McGill University
PIRSA:13120037
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Rebuilding Mathematics on a Quantum Logical Foundation
Richard deJonghe University of Illinois at Chicago
It is not unnatural to expect that difficulties lying at the foundations of quantum mechanics can only be resolved by literally going back and rethinking the quantum theory from first principles (namely, the principles of logic). In this talk, I will present a first-order quantum logic which generalizes the propositional quatum logic originated by Birkhoff and von Neumann as well as the standard classical predicate logic used in the development of virtually all of modern mathematics. I will then use this quantum logic to begin to build the foundations of a new ``quantum mathematics'' --- in particular a quantum set theory and a quantum arithmetic --- which has the potential to provide a completely new mathematical framework in which to develop the theory of quantum
mechanics. -
(0,2) Trialities
Abhijit Gadde Stony Brook University
Motivated by the connection between 4-manifolds and 2d N=(0,2) theories, we study the dynamics of a fairly large class of 2d N=(0,2) gauge theories. We see that physics of such theories is very rich, much as the physics of 4d N=1 theories. We discover a new type of duality that is very reminiscent of the 4d Seiberg duality. Surprisingly, the new 2d duality is an operation of order three. We study the low energy physics and use elliptic genus to detect dynamical supersymmetry breaking. -
Consistency of Massive Gravity
Lavinia Heisenberg ETH Zurich
Recently there has been a successful non-linear covariant ghost-free generalization of Fierz-Pauli massive gravity theory, the dRGT theory. I will explore the cosmology in the decoupling limit of this theory. Furthermore, I will construct a Proxy theory to dRGT from the decoupling limit and study the cosmology there as well and compare the results. Finally, I will discuss the quantum consistency of the theory. -
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No GUTs, All Glory: Charge Quantization and the Standard Model from Nonlinear Sigma Models
John Kehayias University of Tokyo
I will present recent and ongoing work in collaboration with Tsutomu Yanagida and Simeon Hellerman (arXiv:1309.0692 and 1312.xxxx) on a new way to obtain charge quantization, without a GUT or monopole solution. In the CP^1 model, SU(2)_G/U(1)_H, consistency conditions for a charged field and its transformation properties over the entire group manifold lead to a charge quantization condition. By gauging the U(1)_H and identifying it with hypercharge, we find charge quantization in the SM without a monopole or GUT, purely from the structure and dynamics of the nonlinear sigma model. This is easily extended to CP^2 and general CP^k models. Phenomenologically, the CP^1 model has a fractionally charged stable Nambu-Goldstone boson (NGB), which has intriguing applications to nuclear physics and dark matter. The CP^2 model has the Higgs as the NGB. With some additional minor assumptions, anomaly freedom then leads to the matter content of a generation in the SM. -
Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice
Gang Chen Fudan University
Quantum spin liquid (QSL) is an exotic phase of matter and provides an interesting example of emergent non-locality. Even though many materials have been proposed as candidates for QSLs, there is no direct confirmation of QSLs in any of these systems. Quantum spin ice (QSI) is a physical realization of U(1) QSLs on the pyrochlore lattice. We consider a class of electron systems in which dipolar-octupolar Kramers doublets arise on the pyrochlore lattice. In the localized limit, the Kramers doublets are described by the effective spin 1/2 pseudospins. The most general nearest-neighbor exchange model between these pseudospins is the XYZ model. We show that this XYZ model exhibit two distinct symmetry enriched QSI phases, that we dub dipolar QSI and octupolar QSI. This XYZ model is absent from the notorious sign problem for a quantum Monte Carlo simmulation. We also discuss the potential relevance to real material systems. -
Calculating the free energy of antimicrobial peptide (HHC-36) dimerization in bulk
shaqa vafa University of Guelph
PIRSA:13120043The increasing demand for antibiotics has contributed to the investigation of possible novel antibiotics by many researchers. For this purpose experimental and theoretical studies have been carried out to draw scientists' attention to antimicrobial peptides and their interaction with the surface of bacterial membranes. Their ability to disrupt the functioning of bacterial membranes has been probed from different perspectives. The most desirable antimicrobial peptides are those which do not harm plant or animals' membranes but which disrupt bacterial membranes. It has been found that some cationic antimicrobial peptides (CAPs) satisfy these requirements. CAPs interacting with the outer membrane of gram-negative bacteria and the membrane of gram-positive bacteria have been studied recently.We conduct a Molecular Dynamics simulation study of peptide-peptide interactions in physiological solutions and investigate the mechanism of CAPs aggregation since aggregation of the peptides could precede their interaction with the membrane. Different algorithms are applied to calculate the potential mean force of the aggregation process of peptides to select the most efficient one. Also we have run CD spectroscopy and calorimetry experiments to predict the structure of the peptide and measure the peptide-peptide binding enthalpy and compared these results with our simulation data. The particular CAP studied is HHC-36 a peptide selected by high throughput screening (A. Cherkasov et al ACS Chem. Biol. 2009 4 (1) pp 6574) (M. Kazemzadeh-Narbat et al Biomed. Mater. Res. Part B 2012 5 pp1344-1352) (M. Ma et al Biomed. Mater. Res. Part A 2012 2 pp278-185) which has nine amino acid residues and charge +5. -
Ab initio insight in supercooled water
John Tatini Titantah Western University
PIRSA:13120042As an extension to previous ab initio studies on water [12] we present 400 psBorn-Oppenheimer ab initio Molecular dynamics study on water at deep supercooled temperatures (down to 220 K) and confirm a crossover from a fragile to strongliquid around the Widom line. This crossover is accompanied by the passage from relatively weaker hydrogen bonds in the dominantly high density liquid (HDL) at high temperatures to strong hydrogen bond in dominantly low density liquid (LDL). This crossover is accompanied by a maximum in the excess specific heat at constant volume and may lend further support to the existence of a liquid-liquid critical point (LLCP) in supercooled water as was predicted by Peter Poole and collaborators using ST2 water model[3].References[1] J. T. Titantah and M. Karttunen Long-Time Correlations and Hydrophobe-Modified Hydrogen-Bonding Dynamics in Hydrophobic Hydration. J. Am. Chem. Soc. 134 9362 (2012)[2] J. T. Titantah and M. Karttunen Water dynamics: Relation between hydrogen bond bifurcations molecular jumps local density & hydrophobicity. Sci. Rep. 3 2991 (2013)[3] Poole P. H. Sciortino F. Essmann U. & Stanley H. E. Phase behaviour of metastable water. Nature 360 324328 (1992) -
Budding transition of a self-avoiding polymer confined by a soft membrane adhering onto a flat wall
Yu-Cheng Su University of Waterloo
PIRSA:13120041Monte Carlo simulation is used to study the structural properties of the system consisting of a self-avoiding polymer chain confined between a fluid membrane and a flat hard surface. As the adhesion between the soft membrane and the hard-wall surface increases the polymer is subject to a strong confinement; a pancake-shaped polymer conformation state eventually yields to a bud state through an abrupt first-order phase transition. We explore the scaling behavior of the physical properties of the system as functions of the polymers size the membranes surface tension and the adhesion energy for both pancake and bud states in terms of Monte Carlo data and analytic scaling theories. -
Dynamical simulation of disordered micelles in a diblock copolymer melt with fluctuations
Russell Spencer University of Guelph
PIRSA:13120040By including composition fluctuations in our dynamical simulation of the time-dependent Landau-Brazovskii model for a diblock copolymer melt we find that disordered micelles form above the order-disorder transition to a BCC phase. At high-temperatures the micelle number density and volume fraction are effectively zero and the melt is disordered at the molecular level. As we lower the temperature the micelle number density increases gradually and approaches the number density in the BCC phase. If we increase the strength of the fluctuations the temperature range over which disordered micelles exist broadens and the onset of BCC order is suppressed. By tracking trajectories we also investigate the dynamical behaviour of individual micelles in an environment of disordered micelles We find diffusive behaviour which we investigate as a function of temperature and micelle volume fraction. -
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Phase-field model for cellular monolayers : a cancer cell migration studyauthors : Benoit Palmieri and Martin Grant
Benoit Palmieri McGill University
PIRSA:13120037Recent experimental work [1] suggests that the increased motility of cancer cells observed in a confluent monolayer of normal cells is due to the mechanical mismatch between the two cell types. The soft cancer cell undergoes large deformations and can squeeze between small channels defined by the space between the normal cells. We developed a phase-field model description of cellular monolayers to study such a process. The system is setup as a free-boundary problem where each cell is a highly deformable soft body [2]. The motion of each cell is described by a persistent random walk where the velocities and persistent times can be obtained from experimental observations. Our model is used to test the hypothesis that the mechanical mismatch alone increases the motility of softer cells when all other parameters are the same.[1] Lee et al. Biophys. J. vol. 102 p. 2731 (2012).[2] Najem et al. Europhys. Lett. vol. 102 p. 16001 (2013).