14,364 research outputs found

    Quantum shutter approach to tunneling time scales with wave packets

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    The quantum shutter approach to tunneling time scales (G. Garc\'{\i }a-Calder\'{o}n and A. Rubio, Phys. Rev. A \textbf{55}, 3361 (1997)), which uses a cutoff plane wave as the initial condition, is extended in such a way that a certain type of wave packet can be used as the initial condition. An analytical expression for the time evolved wave function is derived. The time-domain resonance, the peaked structure of the probability density (as the function of time) at the exit of the barrier, originally found with the cutoff plane wave initial condition, is studied with the wave packet initial conditions. It is found that the time-domain resonance is not very sensitive to the width of the packet when the transmission process is in the tunneling regime.Comment: 6 page

    Unbinding Transition Induced by Osmotic Pressure in Relation to Unilamellar Vesicle Formation

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    Small-angle X-ray scattering and phase-contrast microscopy experiments were performed to investigate the effect of the osmotic pressure on vesicle formation in a dioleoylphosphatidylcholine (DOPC)/water/NaI system. Multi-lamellar vesicles were formed when a pure lipid film was hydrated with an aqueous solution of NaI. On the other hand, uni-lamellar vesicles (ULVs) were formed when a lipid film mixed with an enough amount of NaI was hydrated. To confirm the effect of the osmotic pressure due to NaI, a free-energy calculation was performed. This result showed that the osmotic pressure induced an unbinding transition on the hydration process, which resulted in ULV formation

    A Search for H-alpha Absorption in the Exosphere of the Transiting Extrasolar Planet HD 209458b

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    There is evidence that the transiting planet HD 209458b has a large exosphere of neutral hydrogen, based on a 15% decrement in Lyman-alpha flux that was observed by Vidal-Madjar et al. during transits. Here we report upper limits on H-alpha absorption by the exosphere. The results are based on optical spectra of the parent star obtained with the Subaru High Dispersion Spectrograph. Comparison of the spectra taken inside and outside of transit reveals no exospheric H-alpha signal greater than 0.1% within a 5.1A band (chosen to have the same Delta_lambda/lambda as the 15% Ly-alpha absorption). The corresponding limit on the column density of n=2 neutral hydrogen is N_2 <~ 10^9 cm^{-2}. This limit constrains proposed models involving a hot (~10^4 K) and hydrodynamically escaping exosphere.Comment: To appear in PASJ [9 pages, 5 figures]. Minor corrections to match published versio

    Universality in heavy-fermion systems with general degeneracy

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    We discuss the relation between the T^{2}-coefficient of electrical resistivity AA and the T-linear specific-heat coefficient γ\gamma for heavy-fermion systems with general NN, where NN is the degeneracy of quasi-particles. A set of experimental data reveals that the Kadowaki-Woods relation; A/γ2=1105μΩ(Kmol/mJ)2A/\gamma^{2} = 1*10^{-5} {\mu\Omega}(K mol/mJ)^{2}, collapses remarkably for large-N systems, although this relation has been regarded to be commonly applicable to the Fermi-liquids. Instead, based on the Fermi-liquid theory we propose a new relation; A~/γ~2=1×105\tilde{A}/\tilde{\gamma}^2=1\times10^{-5} with A~=A/(1/2)N(N1)\tilde{A} = A/(1/2)N(N-1) and γ~=γ/(1/2)N(N1)\tilde{\gamma} = \gamma/(1/2)N(N-1). This new relation exhibits an excellent agreement with the data for whole the range of degenerate heavy-fermions.Comment: 2 figures, to appear in Phys. Rev. Let

    Mesoscopic Phase Fluctuations: General Phenomenon in Condensed Matter

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    General conditions for the occurrence of mesoscopic phase fluctuations in condensed matter are considered. The description of different thermodynamic phases, which coexist as a mixture of mesoscopically separated regions, is based on the {\it theory of heterophase fluctuations}. The spaces of states, typical of the related phases, are characterized by {\it weighted Hilbert spaces}. Several models illustrate the main features of heterophase condensed matter.Comment: 23 pages, Latex, no figure