27,409 research outputs found
Induced top Yukawa coupling and suppressed Higgs mass parameters
In the scenarios with heavy top squarks, mass parameters of the Higgs field
must be fine-tuned due to a large logarithmic correction to the soft scalar
mass. We consider a new possibility that the top Yukawa coupling is small above
TeV scale. The large top mass is induced from strong Yukawa interaction of the
Higgs with another gauge sector, in which supersymmetry breaking parameters are
given to be small. Then it is found that the logarithmic correction to the
Higgs soft scalar mass is suppressed in spite of the strong coupling and the
fine-tuning is ameliorated. We propose an explicit model coupled to a
superconformal gauge theory which realizes the above situation.Comment: RevTeX4 style, 10 pages, 3 figure
Preparations of methoxynitrophenazines and their photoconductivities
Eight methoxynitrophenazines with a methoxy group at the 1 or 2 position and a nitro group at the 6-, 7-, 8- or 9-position of the phenazine ring 1,6, 1,7. 1,8, 1,9, 2,6, 2,7, 2,8 and 2,9 were prepared and their photocurrents were measured by illuminating the surface-type cell with white light from a W lamp under a N atmosphere at room temp. The photocurrents of 1-nitrophenazine 6 and 2-nitrophenazine 7 are compared with those of the methoxynitrophenazines. The photocurrent (i sub p) increases with increasing light intensity (I), thus satisfying log i varies as n log I. The n values are 0.5-1.0. When the nitro group is located at the beta-position of the phenazine ring, the photocurrent becomes larger owing to the electron withdrawing property of the nitro group. On the other hand, the photocurrents of phenazines with the nitro group at the Alpha-position are extremely small. The photoconductivities of methoxynitrophenazines are lower in air
Electronic structure of CaSrVO: a tale of two energy-scales
We investigate the electronic structure of CaSrVO using
photoemission spectroscopy. Core level spectra establish an electronic phase
separation at the surface, leading to distinctly different surface electronic
structure compared to the bulk. Analysis of the photoemission spectra of this
system allowed us to separate the surface and bulk contributions. These results
help us to understand properties related to two vastly differing energy-scales,
namely the low energy-scale of thermal excitations (~) and the
high-energy scale related to Coulomb and other electronic interactions.Comment: 4 pages and 3 figures. Europhysics Letters (appearing
Quantum secret sharing based on modulated high-dimensional time-bin entanglement
We propose a new scheme for quantum secret sharing (QSS) that uses a
modulated high-dimensional time-bin entanglement. By modulating the relative
phase randomly by {0,pi}, a sender with the entanglement source can randomly
change the sign of the correlation of the measurement outcomes obtained by two
distant recipients. The two recipients must cooperate if they are to obtain the
sign of the correlation, which is used as a secret key. We show that our scheme
is secure against intercept-and-resend (I-R) and beam splitting attacks by an
outside eavesdropper thanks to the non-orthogonality of high-dimensional
time-bin entangled states. We also show that a cheating attempt based on an I-R
attack by one of the recipients can be detected by changing the dimension of
the time bin entanglement randomly and inserting two "vacant" slots between the
packets. Then, cheating attempts can be detected by monitoring the count rate
in the vacant slots. The proposed scheme has better experimental feasibility
than previously proposed entanglement-based QSS schemes.Comment: To appear in Phys. Rev.
Fermi Surface of 3d^1 Perovskite CaVO3 Near the Mott Transition
We present a detailed de Haas van Alphen effect study of the perovskite
CaVO3, offering an unprecedented test of electronic structure calculations in a
3d transition metal oxide. Our experimental and calculated Fermi surfaces are
in good agreement -- but only if we ignore large orthorhombic distortions of
the cubic perovskite structure. Subtle discrepancies may shed light on an
apparent conflict between the low energy properties of CaVO3, which are those
of a simple metal, and high energy probes which reveal strong correlations that
place CaVO3 on the verge of a metal-insulator transition.Comment: 4 pages, 4 figures (REVTeX
Tunnel magnetoresistance and interfacial electronic state
We study the relation between tunnel magnetoresistance (TMR) and interfacial
electronic states modified by magnetic impurities introduced at the interface
of the ferromagnetic tunnel junctions, by making use of the periodic Anderson
model and the linear response theory. It is indicated that the TMR ratio is
strongly reduced depending on the position of the -levels of impurities,
based on reduction in the spin-dependent -electron tunneling in the majority
spin state. The results are compared with experimental results for Cr-dusted
ferromagnetic tunnel junctions, and also with results for metallic multilayers
for which similar reduction in giant magnetoresistance has been reported.Comment: 5 pages, 4 figures, 2 column revtex4 format, ICMFS 2002 (Kyoto
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