222 research outputs found

    Fermion Masses and Mixings in GUTs with Non-Canonical U(1)_Y

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    We discuss fermion masses and mixings in models derived from orbifold GUTs such that gauge coupling unification is achieved without low energy supersymmetry by utilizing a non-canonical U(1)_Y. A gauged U(1)_X flavor symmetry plays an essential role, and the Green-Schwarz mechanism is invoked in anomaly cancellations. Models containing vector-like particles with masses close to M_{GUT} are also discussed.Comment: 18 page

    Measurables of CPCP Violation in Bd→DCP0KSB_d\to D^0_{CP}K_S at a BB-meson Factory

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    In the context of the standard electroweak model, we emphasize that Bd→DCP0KSB_d\rightarrow D^0_{CP}K_S (DCP0D^0_{CP} denotes a CPCP eigenstate of D0D^0 or Dˉ0\bar{D}^0) can compete with Bd→π+π−B_d\rightarrow \pi^+\pi^- in studying CPCP violation and probing the Cabibbo-Kobayashi-Maskawa unitarity triangle. We discuss the measurables of direct and indirect CPCP asymmetries in Bd0B^0_d vs Bˉd0→DCP0KS\bar{B}^0_d\rightarrow D^0_{CP}K_S under the circumstance of an asymmetric BB-meson factory running on the Υ(4S)\Upsilon(4S) resonance, and show that both the weak and strong phases are experimentally determinable even in the presence of unknown final-state interactions.Comment: 6 Postscript pages, accepted for publication in IL Nuovo Cimento A as a "Note Brevi

    Magneto-ionic control of interfacial magnetism

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    In metal/oxide heterostructures, rich chemical electronic magnetic and mechanical properties can emerge from interfacial chemistry and structure. The possibility to dynamically control interface characteristics with an electric field paves the way towards voltage control of these properties in solid-state devices. Here, we show that electrical switching of the interfacial oxidation state allows for voltage control of magnetic properties to an extent never before achieved through conventional magneto-electric coupling mechanisms. We directly observe in situ voltage-driven O{superscript 2−] migration in a ​Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic anisotropy energy by >0.75 erg cm[superscript −2] at just 2 V. We exploit the thermally activated nature of ion migration to markedly increase the switching efficiency and to demonstrate reversible patterning of magnetic properties through local activation of ionic migration. These results suggest a path towards voltage-programmable materials based on solid-state switching of interface oxygen chemistry.National Science Foundation (U.S.) (NSF-ECCS-1128439)National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (DMR-0819762)Samsung (Firm) (Samsung Global MRAM Innovation program

    Effects of communication and utility-based decision making in a simple model of evacuation

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    We present a simple cellular automaton based model of decision making during evacuation. Evacuees have to choose between two different exit routes, resulting in a strategic decision making problem. Agents take their decisions based on utility functions, these can be revised as the evacuation proceeds, leading to complex interaction between individuals and to jamming transitions. The model also includes the possibility to communicate and exchange information with distant agents, information received may affect the decision of agents. We show that under a wider range of evacuation scenarios performance of the model system as a whole is optimal at an intermediate fraction of evacuees with access to communication.Comment: 9 pages, 9 figure

    A Multimodality Hybrid Gamma-Optical Camera for Intraoperative Imaging

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    The development of low profile gamma-ray detectors has encouraged the production of small field of view (SFOV) hand-held imaging devices for use at the patient bedside and in operating theatres. Early development of these SFOV cameras was focussed on a single modality-gamma ray imaging. Recently, a hybrid system-gamma plus optical imaging-has been developed. This combination of optical and gamma cameras enables high spatial resolution multi-modal imaging, giving a superimposed scintigraphic and optical image. Hybrid imaging offers new possibilities for assisting clinicians and surgeons in localising the site of uptake in procedures such as sentinel node detection. The hybrid camera concept can be extended to a multimodal detector design which can offer stereoscopic images, depth estimation of gamma-emitting sources, and simultaneous gamma and fluorescence imaging. Recent improvements to the hybrid camera have been used to produce dual-modality images in both laboratory simulations and in the clinic. Hybrid imaging of a patient who underwent thyroid scintigraphy is reported. In addition, we present data which shows that the hybrid camera concept can be extended to estimate the position and depth of radionuclide distribution within an object and also report the first combined gamma and Near-Infrared (NIR) fluorescence images.Peer-reviewedPublisher Versio

    Completely Positive Maps and Classical Correlations

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    We expand the set of initial states of a system and its environment that are known to guarantee completely positive reduced dynamics for the system when the combined state evolves unitarily. We characterize the correlations in the initial state in terms of its quantum discord [H. Ollivier and W. H. Zurek, Phys. Rev. Lett. 88, 017901 (2001)]. We prove that initial states that have only classical correlations lead to completely positive reduced dynamics. The induced maps can be not completely positive when quantum correlations including, but not limited to, entanglement are present. We outline the implications of our results to quantum process tomography experiments.Comment: 4 pages, 1 figur
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