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Articles 1 - 8 of 8
Full-Text Articles in Physics
Experimental Characterization Of Coherent Magnetization Transport In A One-Dimensional Spin System, Chandrasekhar Ramanathan, Paola Cappellaro, Lorenza Viola, David G. Cory
Experimental Characterization Of Coherent Magnetization Transport In A One-Dimensional Spin System, Chandrasekhar Ramanathan, Paola Cappellaro, Lorenza Viola, David G. Cory
Dartmouth Scholarship
We experimentally characterize the non-equilibrium, room-temperature magnetization dynamics of a spin chain evolving under an effective double-quantum (DQ) Hamiltonian. We show that the Liouville space operators corresponding to the magnetization and the two-spin correlations evolve 90 degrees out of phase with each other, and drive the transport dynamics. For a nearest-neighbor-coupled N-spin chain, the dynamics are found to be restricted to a Liouville operator space whose dimension scales only as N2, leading to a slow growth of multi-spin correlations. Even though long-range couplings are present in the real system, we find excellent agreement between the analytical predictions …
The Hyperspherical Four-Fermion Problem, Seth T. Rittenhouse, J Von Stecher, J P. D'Incao, Nirav P. Mehta, Chris H. Greene
The Hyperspherical Four-Fermion Problem, Seth T. Rittenhouse, J Von Stecher, J P. D'Incao, Nirav P. Mehta, Chris H. Greene
Physics and Astronomy Faculty Research
The problem of a few interacting fermions in quantum physics has sparked intense interest, particularly in recent years owing to connections with the behaviour of superconductors, fermionic superfluids and finite nuclei. This review addresses recent developments in the theoretical description of four fermions having finite-range interactions, stressing insights that have emerged from a hyperspherical coordinate perspective. The subject is complicated, so we have included many detailed formulae that will hopefully make these methods accessible to others interested in using them. The universality regime, where the dominant length scale in the problem is the two-body scattering length, is particularly stressed, including …
The Quantum Dialectic, Logan Kelley
The Quantum Dialectic, Logan Kelley
Pitzer Senior Theses
A philosophic account of quantum physics. The thesis is divided into two parts. Part I is dedicated to laying the groundwork of quantum physics, and explaining some of the primary difficulties. Subjects of interest will include the principle of locality, the quantum uncertainty principle, and Einstein's criterion for reality. Quantum dilemmas discussed include the double-slit experiment, observations of spin and polarization, EPR, and Bell's theorem. The first part will argue that mathematical-physical descriptions of the world fall short of explaining the experimental observations of quantum phenomenon. The problem, as will be argued, is framework of the physical descriptive schema. Part …
Dynamical Critical Scaling And Effective Thermalization In Quantum Quenches: Role Of The Initial State, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Dynamical Critical Scaling And Effective Thermalization In Quantum Quenches: Role Of The Initial State, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Dartmouth Scholarship
We explore the robustness of universal dynamical scaling behavior in a quantum system near criticality with respect to initialization in a large class of states with finite energy. By focusing on a homogeneous XY quantum spin chain in a transverse field, we characterize the nonequilibrium response under adiabatic and sudden quench processes originating from a pure as well as a mixed excited initial state, and involving either a regular quantum critical or a multicritical point. We find that the critical exponents of the ground-state quantum phase transition can be encoded in the dynamical scaling exponents despite the finite energy of …
Static And Dynamic Casimir Effect Instabilities, Y. N. Srivastava, A. Widom, S. Sivasubramanian, M. Pradeep Ganesh
Static And Dynamic Casimir Effect Instabilities, Y. N. Srivastava, A. Widom, S. Sivasubramanian, M. Pradeep Ganesh
Allan Widom
The static Casimir effect concerns quantum electrodynamic induced Lamb shifts in the mode frequencies and thermal free energies of condensed matter systems. Sometimes, the condensed matter constitutes the boundaries of a vacuum region. The static frequency shift effects have been calculated in the one photon loop perturbation theory approximation. The dynamic Casimir effect concerns two photon radiation processes arising from time dependent frequency modulations again computed in the one photon loop approximation. Under certain conditions the one photon loop computation may become unstable and higher order terms must be invoked to achieve stable solutions. This stability calculation is discussed for …
Acuasal Behavior In Quantum Electrodynamics, A. Widom, Y. N. Srivastava, E. Sassaroli
Acuasal Behavior In Quantum Electrodynamics, A. Widom, Y. N. Srivastava, E. Sassaroli
Allan Widom
Acausal features of quantum electrodynamic processes are discussed. While these processes are not present for the classical electrodynamic theory, in the quantum electrodynamic theory, acausal processes are well known to exist. For example, any Feynman diagram with a "loop" in space-time describes a "particle" which may move forward in time or backward in time or in space-like directions. The engineering problems involved in experimentally testing such causality violations on a macroscopic scale are explored.
Causality And Electromagnetic Transmissions Through Materials, V. Kidambi, A. Widom
Causality And Electromagnetic Transmissions Through Materials, V. Kidambi, A. Widom
Allan Widom
There have been several experiments which hint at evidence for superluminal transport of electromagnetic energy through a material slab. On the theoretical side, it has appeared evident that acausal signals are indeed possible in quantum electrodynamics. However, it is unlikely that superluminal signals can be understood on the basis of a purely classical electrodynamic signals passing through a material. The classical and quantum theories represent quite different views, and it is the quantum view which may lead to violations of Einstein causality.
Hamiltonian Dynamics In The Theory Of Abstraction, Subhajit Kumar Ganguly
Hamiltonian Dynamics In The Theory Of Abstraction, Subhajit Kumar Ganguly
Subhajit Kumar Ganguly
This paper deals with fluid flow dynamics which may be Hamiltonian in nature and yet chaotic.Here we deal with sympletic invariance, canonical transformations and stability of such Hamiltonian flows. As a collection of points move along, it carries along and distorts its own neighbourhood. This in turn affects the stability of such flows.