27,492 research outputs found

    Coherent States on Hilbert Modules

    Full text link
    We generalize the concept of coherent states, traditionally defined as special families of vectors on Hilbert spaces, to Hilbert modules. We show that Hilbert modules over C∗C^*-algebras are the natural settings for a generalization of coherent states defined on Hilbert spaces. We consider those Hilbert C∗C^*-modules which have a natural left action from another C∗C^*-algebra say, A\mathcal A. The coherent states are well defined in this case and they behave well with respect to the left action by A\mathcal A. Certain classical objects like the Cuntz algebra are related to specific examples of coherent states. Finally we show that coherent states on modules give rise to a completely positive kernel between two C∗C^*-algebras, in complete analogy to the Hilbert space situation. Related to this there is a dilation result for positive operator valued measures, in the sense of Naimark. A number of examples are worked out to illustrate the theory

    Multiple classical limits in relativistic and nonrelativistic quantum mechanics

    Full text link
    The existence of a classical limit describing interacting particles in a second-quantized theory of identical particles with bosonic symmetry is proved. This limit exists in addition to a previously established classical limit with a classical field behavior, showing that the limit ℏ→0\hbar \to 0 of the theory is not unique. An analogous result is valid for a free massive scalar field: two distinct classical limits are proved to exist, describing a system of particles or a classical field. The introduction of local operators in order to represent kinematical properties of interest is shown to break the permutation symmetry under some localizability conditions, allowing the study of individual particle properties.Comment: 13 page

    Supersymmetric Effects on Isospin Symmetry Breaking and Direct CP Violation in Bâ†’ÏÎłB \to \rho \gamma

    Full text link
    We argue that one can search for physics beyond the standard model through measurements of the isospin-violating quantity Δ−0≡Γ(Bâˆ’â†’Ïâˆ’Îł)/2Γ(B0→ρ0Îł)−1\Delta^{-0} \equiv \Gamma(B^- \to \rho^- \gamma)/2\Gamma(B^0 \to \rho^0 \gamma)-1, its charge conjugate Δ+0\Delta^{+0}, and direct CP violation in the partial decay rates of BÂ±â†’ÏÂ±ÎłB^\pm \to \rho^\pm \gamma. We illustrate this by working out theoretical profiles of the charge-conjugate averaged ratio Δ≡12(Δ+0+Δ−0)\Delta \equiv {1 \over 2}(\Delta^{+0} +\Delta^{-0}) and the CP asymmetry ACP(BÂ±â†’ÏÂ±Îł)A_{CP}(B^\pm \to \rho^\pm \gamma) in the standard model and in some variants of the minimal supersymmetric standard model. We find that chargino contributions in the large tan⁥ÎČ\tan \beta region may modify the magnitudes and flip the signs of Δ\Delta and ACP(BÂ±â†’ÏÂ±Îł)A_{CP}(B^\pm \to \rho^\pm \gamma) compared to their standard-model values, providing an unmistakeable signature of supersymmetry.Comment: 10 pages, 7 figures (requires graphicx

    Quantum Transport with Spin Dephasing: A Nonequilibrium Green's Function Approach

    Full text link
    A quantum transport model incorporating spin scattering processes is presented using the non-equilibrium Green's function (NEGF) formalism within the self-consistent Born approximation. This model offers a unified approach by capturing the spin-flip scattering and the quantum effects simultaneously. A numerical implementation of the model is illustrated for magnetic tunnel junction devices with embedded magnetic impurity layers. The results are compared with experimental data, revealing the underlying physics of the coherent and incoherent transport regimes. It is shown that small variations in magnetic impurity spin-states/concentrations could cause large deviations in junction magnetoresistances.Comment: NEGF Formalism, Spin Dephasing, Magnetic Tunnel Junctions, Magnetoresistanc

    Pengaruh Konsentrasi Mutagen Sodium Azida (Nan3) terhadap Daya Kecambah dan Keragaan Bibit Padi Gogo Varietas Kulit Manis Generasi M-1

    Full text link
    This experiment aims to observe the effect of mutagen concentration of sodium azide to the germination and seedling growth performance of upland rice varieties Kulit Manis generation M-1 and the difference in seedling growth of upland rice varieties in Kulit Manis on the generation M-1 by application Sodium Azide some mutagen concentration. The experiment was conducted in an area behind the of Soil Laboratory, Faculty of Agriculture, University of Riau, from May to July 2015. Research was arranged experimentally using Completely Randomized Design, which consists of 5 treatments concentration of sodium azide (SA), ie (0.0, 0.5, 1.0, 1.5 and 2.0 mM). The mean deviation between treatments tested by Duncan New Multiple Range Test (DNMRT) at the level of 5%. Parameters observed were the first count test, the soil emergence test and the percentage of life seedlings. The result showed that the concentration of Sodium Azide significantly effected on the first count test, the soil emergence test and life seedling percentage. Sodium Azide at the concentration of 2.0 mM produce the first count test, the soil emergence test and the lowest percentage of life seedling

    Perspectives: Quantum Mechanics on Phase Space

    Full text link
    The basic ideas in the theory of quantum mechanics on phase space are illustrated through an introduction of generalities, which seem to underlie most if not all such formulations and follow with examples taken primarily from kinematical particle model descriptions exhibiting either Galileian or Lorentzian symmetry. The structures of fundamental importance are the relevant (Lie) groups of symmetries and their homogeneous (and associated) spaces that, in the situations of interest, also possess Hamiltonian structures. Comments are made on the relation between the theory outlined and a recent paper by Carmeli, Cassinelli, Toigo, and Vacchini.Comment: "Quantum Structures 2004" - Meeting of the International Quantum Structures Association; Denver, Colorado; 17-22 July, 200

    On the nature of the deeply embedded protostar OMC-2 FIR 4

    Get PDF
    We use mid-infrared to submillimeter data from the Spitzer, Herschel, and APEX telescopes to study the bright sub-mm source OMC-2 FIR 4. We find a point source at 8, 24, and 70 Ό\mum, and a compact, but extended source at 160, 350, and 870 Ό\mum. The peak of the emission from 8 to 70 Ό\mum, attributed to the protostar associated with FIR 4, is displaced relative to the peak of the extended emission; the latter represents the large molecular core the protostar is embedded within. We determine that the protostar has a bolometric luminosity of 37 Lsun, although including more extended emission surrounding the point source raises this value to 86 Lsun. Radiative transfer models of the protostellar system fit the observed SED well and yield a total luminosity of most likely less than 100 Lsun. Our models suggest that the bolometric luminosity of the protostar could be just 12-14 Lsun, while the luminosity of the colder (~ 20 K) extended core could be around 100 Lsun, with a mass of about 27 Msun. Our derived luminosities for the protostar OMC-2 FIR 4 are in direct contradiction with previous claims of a total luminosity of 1000 Lsun (Crimier et al 2009). Furthermore, we find evidence from far-infrared molecular spectra (Kama et al. 2013, Manoj et al. 2013) and 3.6 cm emission (Reipurth et al 1999) that FIR 4 drives an outflow. The final stellar mass the protostar will ultimately achieve is uncertain due to its association with the large reservoir of mass found in the cold core.Comment: Accpeted by ApJ, 17 pages, 11 figure
    • 

    corecore