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Research Interests: Physics and phase diagram
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In this work the connection between vortex condensation in a d-wave superconductor and the QED 3 gauge theory of the pseudogap is elucidated. The approach taken circumvents the use of the standard Franz–Tesanovic gauge transformation,... more
In this work the connection between vortex condensation in a d-wave superconductor and the QED 3 gauge theory of the pseudogap is elucidated. The approach taken circumvents the use of the standard Franz–Tesanovic gauge transformation, borrowing ideas from the path-integral analysis of the Aharonov–Bohm problem. An essential feature of this approach is that gauge transformations which are prohibited on a particular multiply-connected manifold (e.g. a superconductor with vortices) can be successfully performed on the universal covering space associated with that manifold.
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We study an interacting boson gas in a periodic optical potential, with the goal of understanding the properties of such a gas away from the Mott insulating regime at large optical lattice depth. In particular, we analyze the density... more
We study an interacting boson gas in a periodic optical potential, with the goal of understanding the properties of such a gas away from the Mott insulating regime at large optical lattice depth. In particular, we analyze the density dependence of the transition temperature as a function of optical lattice depth and the response to a dynamical modulation of the
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Research Interests: Physics, Theoretical Physics, Superfluidity, Atomic Physics, Atomic and Molecular Physics, and 10 moreBose Einstein Condensation, Mathematical Sciences, Physical sciences, Ultracold Quantum Gases, Cold Atoms Physics, Bose Hubbard Model, CHEMICAL SCIENCES, Hartree fock method, Boson, and Interacting Boson Model
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By exploiting a recent breakthrough in the growth of YBa_2Cu_3O_6+x, carrier doping can be tuned by room temperature annealing, across a 20 K range of transition temperature near the boundary of superconductivity and antiferromagnetism.... more
By exploiting a recent breakthrough in the growth of YBa_2Cu_3O_6+x, carrier doping can be tuned by room temperature annealing, across a 20 K range of transition temperature near the boundary of superconductivity and antiferromagnetism. Experiments carried out on these samples at microwave and radio frequencies have been used to obtain the doping and temperature dependence of the magnetic penetration depth.
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We study an s-wave resonant Fermi gas near the unitarity point. We treat this problem by generalizing the Fermi gas to a model with 2N hyperfine states (with Sp(2N) symmetry). We show that for N=∞, the model can be solved exactly by the... more
We study an s-wave resonant Fermi gas near the unitarity point. We treat this problem by generalizing the Fermi gas to a model with 2N hyperfine states (with Sp(2N) symmetry). We show that for N=∞, the model can be solved exactly by the BEC-BCS mean field solution. In order to address the physically relevant problem (N=1), we perform a systematic
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The topological structure of the order parameter in Zhang{close_quote}s SO(5) theory of superconductivity allows for an unusual type of dissipation mechanism by which current-carrying states can decay. The resistivity due to this... more
The topological structure of the order parameter in Zhang{close_quote}s SO(5) theory of superconductivity allows for an unusual type of dissipation mechanism by which current-carrying states can decay. The resistivity due to this mechanism, which involves orientation rather than amplitude order-parameter fluctuations, is calculated for the case of a thin superconducting wire. The approach is a suitably modified version of that pioneered by Langer and Ambegaokar for conventional superconductors. {copyright} {ital 1998} {ital The American Physical Society}
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The response to the dynamical modulation of optical lattice potentials is studied by Determinantal Quantum Monte Carlo combined with the Maximum Entropy method. We simulate three and two-dimensional repulsive fermionic Hubbard models... more
The response to the dynamical modulation of optical lattice potentials is studied by Determinantal Quantum Monte Carlo combined with the Maximum Entropy method. We simulate three and two-dimensional repulsive fermionic Hubbard models within the strong coupling regime ...
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... Corri-do poets often initiate their songs with a plea, "Senores perdonaran," (Gen-tlemen, forgive me) and sometimes add for good measure, "no se vayan a... more
... Corri-do poets often initiate their songs with a plea, "Senores perdonaran," (Gen-tlemen, forgive me) and sometimes add for good measure, "no se vayan a enojar" (do not become angry). And I will take another phrase from ...
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This paper describes research into the development of a quality plan for the management of software in an Irish Hospital. It studies relevant standards, models and legal acts. Synergies between the Irish Health Service Executive's... more
This paper describes research into the development of a quality plan for the management of software in an Irish Hospital. It studies relevant standards, models and legal acts. Synergies between the Irish Health Service Executive's Quality and Risk Management Standard and the Capability Maturity Model Integration are utilised to build and study a quality plan. While exploring the possibility of utilising software engineering quality standards to improve the quality standards within health care, this has also led to a greater understanding of the ...
We investigate a novel contribution to the low-energy quasiparticle density of states (DOS) of a disordered d-wave superconductor. Related work (C. Pépin and P. A. Lee, Phys. Rev. B 63), 054502 (2001). found that the DOS is singular at... more
We investigate a novel contribution to the low-energy quasiparticle density of states (DOS) of a disordered d-wave superconductor. Related work (C. Pépin and P. A. Lee, Phys. Rev. B 63), 054502 (2001). found that the DOS is singular at zero energy, but it was later argued (A.G. Yashenkin et al., Phys. Rev. Lett. 86), 5982 (2001); A. Altland, cond-mat/0108079 (unpublished).
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In the cuprate superconductor YBa2Cu3O6+x, hole doping in the CuO2 layers is controlled by both oxygen content and the degree of oxygen ordering. At the composition YBa2Cu3O6.35, the ordering can occur at room temperature, thereby tuning... more
In the cuprate superconductor YBa2Cu3O6+x, hole doping in the CuO2 layers is controlled by both oxygen content and the degree of oxygen ordering. At the composition YBa2Cu3O6.35, the ordering can occur at room temperature, thereby tuning the hole doping so that the superconducting critical temperature gradually rises from 0 to 20K. Here we exploit this to study the c^-axis penetration
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We examine the magnetic field dependence of the critical temperature (Tc) for a thin superconducting ring and thin- walled superconducting cylinder (of radius R), in the presence of a magnetic field (B). We include both the orbital effect... more
We examine the magnetic field dependence of the critical temperature (Tc) for a thin superconducting ring and thin- walled superconducting cylinder (of radius R), in the presence of a magnetic field (B). We include both the orbital effect and the Zeeman splitting of the quasiparticle bands. We derive a Ginzburg-Landau free energy functional and allow for the appearance of the
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The polarization noise of small samples of the relaxor ferroelectric Pb1-xLaxZr1-yTiyO3 was studied both in thermal quasiequilibrium and while the applied field was swept. The quasiequilibrium noise obeyed the fluctuation-dissipation... more
The polarization noise of small samples of the relaxor ferroelectric Pb1-xLaxZr1-yTiyO3 was studied both in thermal quasiequilibrium and while the applied field was swept. The quasiequilibrium noise obeyed the fluctuation-dissipation relation. This noise was Gaussian and lacked random features, within experimental resolution. No Barkhausen noise was detected during field sweeps at near-saturating fields. Both those facts point to small coherence