Bulletin of the American Physical Society
2016 Annual Spring Meeting of the APS Ohio-Region Section
Volume 61, Number 5
Friday–Saturday, April 8–9, 2016; Dayton, Ohio
Session D3: Contributed Session III: Particle and Theoretical Physics |
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Chair: Chenglong Zhao, University of Dayton Room: SC119 |
Saturday, April 9, 2016 8:30AM - 8:42AM |
D3.00001: Dissociation transitions for 1D chains and moleculres bound by a general anharmonic interatomic potential Donald Priour Interatomic potentials provide a phenomenological description of atomic interactions, whether in the case of comparatively weak Van der Waals bonding (Lennard Jones) or relatively strong covalent bonding (Morse potential and variants). We consider a general unimodal anharmonic interatomic potential with a well defined minimum, decaying at large distances, and rising sharply if the atomic pair is in close proximity. Under these assumptions, we derive a perturbative series for the partition function, leading to analytical expressions for the mean bond length, the specific heat, and the coefficient of thermal expansion. In this manner, the dissociation transition at low temperature is accurately described as the pressure term becomes small, allowing thermal fluctuations to dissociate a molecule or induce in a 1D chain a crossover from a condensed state to a loosely bound gaseous state. In particular, using exact results to highlight agreement, we show that for dissociation in the low temperature regime, the mean bond length is given by $\langle l \rangle = R_{0}(1 + A \eta^{-2} \varepsilon^{-1/2} e^{-\varepsilon} )$; with $\varepsilon$ and $\eta$ being the dissociation energy and the characteristic pressure energy scale $p R_{0}$ respectively, divided by $k_{\mathrm{B}} T$. [Preview Abstract] |
Saturday, April 9, 2016 8:42AM - 8:54AM |
D3.00002: Interplay of Equipartition and Energy Absorption in Anharmonic Chains with Heated Ends Christopher Watenpool, Donald Priour Whereas vibrational modes in the case of a purely harmonic chain do not interact, thereby preventing equilibration, in principle equipartition becomes feasible if one includes anharmonic terms in the potential. In this vein, we use $V(x) = \alpha x^{2} + \beta x^{4}$. Nevertheless in the case of isolated chains, and in spite of the anharmonicity, the Fermi Pasta Ulam (FPU) phenomena hinders progress toward equipartition at lower temperatures where only long wavelength modes are initially excited. Generically, for large chains, the dominant scaling is $\tau_{\mathrm{eq}} = A N^{\eta}$ with $\eta$ being a scaling exponent. Using the Langevin thermostat prescription applied locally to both ends of the chain, we determine the extent to which allowing energy exchange with a large heat reservoir alters equilibration; while preliminary efforts indicate a modification of the prefactor $A$, we seek to determine if there are temperature regimes where $\eta$ is altered relative to the case of the isolated chain. Having recently observed a temporary but long lived absorption of energy by the system with a concomitant elevation of the chain temperature, we discuss the extent to which the anomalous temperature increase is linked to FPU related effects. [Preview Abstract] |
Saturday, April 9, 2016 8:54AM - 9:06AM |
D3.00003: Unification of Quantum Mechanics and General Relativity: Geometrical Nature of Matter and Multiple Levels of Universes shahram khosravi Spacetimematter is a five dimensional geometry where matter is baked into geometry as a new dimension. Every event point of spacetimematter follows the uncertainty principle, which limits the accuracy of the measurement of its space, time, and matter coordinates turning it into a Space-Time-Matter (STM) geometrical quantum with space, time, and matter edges. The Universe consists of a hierarchical levels of universes where each level has its own level of spacetimematter and quantum state functions. I'll show that non-ordinary matter and energy coming from the non-zeroth levels of universes together form the dark matter and dark energy. I'll present new quantum and general relativity field equations for each level of universe which together unify quantum mechanics and general relativity and the four fundamental forces of nature. I'll then use actual astronomical data and a simple theoretical model to derive the physical constants of the first level of universe and show that they vary from their counterparts in the zeroth level of universe (i.e. ordinary universe). I'll also provide a quantum mechanism for black hole characteristics such as singularity and space-time reversal and show how my approach resolves black hole information paradox. [Preview Abstract] |
Saturday, April 9, 2016 9:06AM - 9:18AM |
D3.00004: How to extract the single-particle content of two-dimensional adjoint QCD Uwe Trittmann The spectrum of two-dimensional adjoint QCD is cluttered with multi-particle states that are uninteresting yet hard to remove. I present some ideas on how to distinguish single- from multi-particle states and discuss the viability of these methods. [Preview Abstract] |
Saturday, April 9, 2016 9:18AM - 9:30AM |
D3.00005: Resolving the Proton Radius Puzzle Using QED-NRQED Effective Field Theory Steven Dye, Matthew Gonderinger, Gil Paz The proton radius puzzle challenges our understanding of the structure of the proton. It can be an indication of a new force that couples to muons, but not to electrons. An effective field theory analysis using Non-Relativistic Quantum Electrodynamics (NRQED) indicates that the muonic hydrogen result can in interpreted as a large, muon-proton spin-independent contact interaction. The muonic hydrogen result can be tested by a muon-proton scattering experiment, MUSE, that is planned at the Paul Scherrer Institute. The typical momenta of the muons in this experiment are of the order of the muon mass. In this energy regime the muons are relativistic but the protons are still non-relativistic. The interaction between the muons and protons can be described by a hybrid QED-NRQED effective field theory. We present some elements of this effective field theory, and compare them previously known results. [Preview Abstract] |
Saturday, April 9, 2016 9:30AM - 9:42AM |
D3.00006: Ultra-High Energy Neutrino Astrophysics with the Askaryan Radio Array Brian Clark Text: We present an overview of the Askaryan Radio Array radio neutrino detector and the elusive cosmic neutrinos for which it searches. Neutrinos, interacting only through the weak force, are immune to photo-hadronic processes that screen photons and massive particles from outside the galaxy. As such, neutrinos are unique portals to ultra-high energy phenomena at cosmic distances, and are essential to our understanding of physics at energy scales beyond those of the LHC. Low cross-sections and low fluxes demand that any search for these particles be of enormous scale. The Askaryan Radio Array, or ARA, is a teraton, $in$-$situ$ ultra-high energy ($>10^{17}$ eV) neutrino detector undergoing phased construction at the South Pole. It searches for these cosmogenic neutrinos by looking for the broadband, impulsive radio-Cerenkov signals that are characteristic of neutrino interactions in dense media. In the radio-clear ice of Antarctica, these pulses travel un-attenuated for kilometers, allowing ARA to instrument the enormous volumes of ice necessary for practical detection. We will present the recently published limits set by ARA for the ultra-high energy neutrino flux between $10^{17}-10^{21}$ eV. [Preview Abstract] |
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