2,682 research outputs found

    Quantization of Black Holes

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    We show that black holes can be quantized in an intuitive and elegant way with results in agreement with conventional knowledge of black holes by using Bohr's idea of quantizing the motion of an electron inside the atom in quantum mechanics. We find that properties of black holes can be also derived from an Ansatz of quantized entropy \Delta S=4\pi k {\Delta R / \lambdabar}, which was suggested in a previous work to unify the black hole entropy formula and Verlinde's conjecture to explain gravity as an entropic force. Such an Ansatz also explains gravity as an entropic force from quantum effect. This suggests a way to unify gravity with quantum theory. Several interesting and surprising results of black holes are given from which we predict the existence of primordial black holes ranging from Planck scale both in size and energy to big ones in size but with low energy behaviors.Comment: Latex 7 pages, no figure

    Isospin violation in Ο•,J/ψ,Οˆβ€²β†’Ο‰Ο€0\phi, J/\psi, \psi^\prime \to \omega \pi^0 via hadronic loops

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    In this work, we study the isospin-violating decay of ϕ→ωπ0\phi\to \omega\pi^0 and quantify the electromagnetic (EM) transitions and intermediate meson exchanges as two major sources of the decay mechanisms. In the EM decays, the present datum status allows a good constraint on the EM decay form factor in the vector meson dominance (VMD) model, and it turns out that the EM transition can only account for about 1/4∼1/31/4\sim 1/3 of the branching ratio for ϕ→ωπ0\phi\to \omega\pi^0. The intermediate meson exchanges, KKΛ‰(Kβˆ—)K\bar{K}(K^*) (intermediate KKΛ‰K\bar{K} interaction via Kβˆ—K^* exchanges), KKβˆ—Λ‰(K)K\bar{K^*}(K) (intermediate KKβˆ—Λ‰K\bar{K^*} rescattering via kaon exchanges), and KKβˆ—Λ‰(Kβˆ—)K\bar{K^*}(K^*) (intermediate KKβˆ—Λ‰K\bar{K^*} rescattering via Kβˆ—K^* exchanges), which evade the naive Okubo-Zweig-Iizuka (OZI) rule, serve as another important contribution to the isospin violations. They are evaluated with effective Lagrangians where explicit constraints from experiment can be applied. Combining these three contributions, we obtain results in good agreement with the experimental data. This approach is also extended to J/ψ(Οˆβ€²)→ωπ0J/\psi(\psi^\prime)\to \omega\pi^0, where we find contributions from the KKΛ‰(Kβˆ—)K\bar{K}(K^*), KKβˆ—Λ‰(K)K\bar{K^*}(K) and KKβˆ—Λ‰(Kβˆ—)K\bar{K^*}(K^*) loops are negligibly small, and the isospin violation is likely to be dominated by the EM transition.Comment: Revised version resubmitted to PRD; Additional loop contributions included; Conclusion unchange

    Magneto-optical properties of semiconductor nanocrystals in glass

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    Understanding of the spin and exciton properties in colloidal nanostructures paves the way for their applications in a variety of fields, such as spintronics and quantum science and technology. Using magneto-optical experimental techniques, the fundamental properties such as polarization, g-factor, spin dynamics in three kind of semiconductor nanocrystals (NCs), i.e. CdSe, CuCl and all-inorganic perovskite (CsPbBr3, CsPbI3) are studied, which help to understand the exciton fine structures and related interac- tions in each material. By combining both the experimental and theoretical efforts, the puzzling behavior of the polarized emission of dark excitons in the ensemble of CdSe NCs is explained by considering the nanocrystal size dispersion and phonon effect. The spin coherent dynamics in the pump-probe measurements show two components, i.e. one oscillating and one nonoscillating. The Larmor frequency from the oscillating component is unambiguously assigned to the electron based on the theoretical analysis. While the nonoscillating component is clarified to be contributed by the frozen exciton spin polarization created by the pump pulse in NCs with heavy-light hole splitting determined by the crystal field. The polarization properties and g-factors in CuCl NCs are investigated comprehensively, where the degree of circular polarization of the Z3 exciton emission is found to increase linearly with the magnetic field at low temperatures up to 8 T. In the spin-flip Raman scattering measurements, a g-factor about 2 is resolved which can be assigned to the electron. The magnetic field and temperature dependent recombination dynamics reveal a dark ground state in both CsPbBr3 and CsPbI3 NCs with corresponding bright-dark exciton splitting being 4.2 meV and 6.5 meV, respectively. In CsPbI3 NCs, very interesting anomalous polarization and spin dynamics are observed, which is related to the interaction between the dark exciton state and the bright exciton fine structure. The spin-flip Raman scattering measurements on CsPbI3 NCs also reveal two g-factors, i.e. one is about 2.5 and another one about 1.5

    Probing scalar meson structures in Ο‡c1\chi_{c1} decays into pseudoscalar and scalar

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    We evaluate the decay branching ratios of χc1→PS\chi_{c1}\to PS, in a quark model parametrization scheme, where PP and SS stand for pseudoscalar and scalar meson, respectively. An interesting feature of this decay process is that the ccˉc\bar{c} annihilate via the pQCD hair-pin diagram is supposed to be dominant. Hence, this decay process should be sensitive to the quark components of the final-state light mesons, and would provide a great opportunity for testing the mixing relations among the scalar mesons, i.e. f0(1370)f_0(1370), f0(1500)f_0(1500) and f0(1710)f_0(1710), by tagging the final state pseudoscalar mesons.Comment: 9 pages and 6 eps figures; Enhanced discussion on the dominance of hair-pin diagram is added. Revised version to appear in IJMP

    Holographic Schwinger effect with a moving D3-brane

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    We study the Schwinger effect with a moving D3-brane in a N\mathcal{N}=4 SYM plasma with the aid of AdS/CFT correspondence. We discuss the test particle pair moving transverse and parallel to the plasma wind respectively. It is found that for both cases the presence of velocity tends to increase the Schwinger effect. In addition, the velocity has a stronger influence on the Schwinger effect when the pair moves transverse to the plasma wind rather than parallel.Comment: 8 pages, 6 figure

    2-[4-(DimethylΒ­amino)phenΒ­yl]imidazo[4,5-f][1,10]phenanthroline sesquihydrate

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    There are two formula units in the asymmetric unit of the title compound, C21H17N5Β·1.5H2O. The imidazo[4,5-f][1,10]phenΒ­anΒ­throline unit is almost coplanar with the benzene ring, the dihedral angles between them being 8.91β€…(5) and 4.93β€…(6)Β° in the two molΒ­ecules. The crystal structure is stabilized by a series of hydrogen bonds between the water molΒ­ecules and the N atoms of the imidazophenanthroline groups

    Probing the nature of Y(4260)Y(4260) and Zc(3900)Z_c(3900) in the isospin violating process Y(4260)β†’J/ΟˆΞ·Ο€0Y(4260) \to J/\psi \eta \pi^0

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    The isospin violation process Y(4260)β†’J/ΟˆΞ·Ο€0Y(4260) \to J/\psi \eta \pi^{0} is studied assuming that Y(4260)Y(4260) is a D1DΛ‰+c.c.D_{1} \bar{D}+c.c. hadronic molecule. In association with the production of the Zc(3900)Z_c(3900), which is treated as a DDΛ‰βˆ—+c.c.D \bar{D}^{*}+c.c. hadronic molecule, this process can help us distinguish their molecular natures from other scenarios, since the incomplete cancellation between the charged and neutral--meson loops, which are prominent in the molecular picture only, produces a peak in the e+eβˆ’β†’Y(4260)β†’J/ΟˆΞ·Ο€0e^+e^-\to Y(4260)\to J/\psi\eta\pi^0 cross section at the D1DΛ‰+c.c.D_{1} \bar{D}+c.c. threshold and a very prominent peak in the J/ψηJ/\psi \eta invariant mass spectrum in between the DDΛ‰βˆ—+c.c.D \bar{D}^{*}+c.c. thresholds; the latter being much narrower than the corresponding one in the isospin conserving channel, i.e. J/ΟˆΟ€+Ο€βˆ’J/\psi \pi^+ \pi^{-}. The partial width of Y(4260)β†’J/ΟˆΞ·Ο€0Y(4260)\to J/\psi\eta\pi^0 is about 4Γ—10βˆ’44 \times 10^{-4} of that of Y(4260)β†’J/ΟˆΟ€+Ο€βˆ’Y(4260)\to J/\psi\pi^+\pi^-. The cross section of e+eβˆ’β†’Y(4260)β†’J/ΟˆΞ·Ο€0e^+e^-\to Y(4260)\to J/\psi\eta\pi^0 at the D1DΛ‰+c.c.D_{1} \bar{D}+c.c. threshold is about 0.05Β pb0.05 \ \mathrm{pb} which is much larger than that produced by the nearby resonances. These features are the direct consequences of the assumed nature of these two states which might be accessible at the high-statistics experiments such as BESIII and LHCb.Comment: 11 pages, 4 figure
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