26,686 research outputs found
Experimental determination of optimum coil pitch for a planar mesh-type micromagnetic sensor
To overcome the directional properties of a planar meander-type sensor, a new planar micromagetic sensor having mesh-type configuration is reported in this paper. Analytical models are usually used for the characterization of the planar-type sensors. Sensors having mesh-type configuration have been fabricated for the derivation of the optimum coil pitch
A light Higgs scenario based on the TeV-scale supersymmetric strong dynamics
We consider a model based on the supersymmetric QCD theory with N_c=2 and
N_f=3. The theory is strongly coupled at the infrared scale \Lambda_H. Its low
energy effective theory below \Lambda_H is described by the supersymmetric
standard model with the Higgs sector that contains four iso-spin doublets, two
neutral iso-spin singlets and two charged iso-spin singlets. If \Lambda_H is at
the multi-TeV to 10 TeV, coupling constants for the F-terms of these composite
fields are relatively large at the electroweak scale. Nevertheless, the SM-like
Higgs boson is predicted to be as light as 125 GeV because these F-terms
contribute to the mass of the SM-like Higgs boson not at the tree level but at
the one-loop level. A large non-decoupling effect due to these F-terms appears
in the one-loop correction to the triple Higgs boson coupling, which amounts to
a few tens percent. Such a non-decoupling property in the Higgs potential
realizes the strong first order phase transition, which is required for a
successful scenario of electroweak baryogenesis
Time-reversible Dynamical Systems for Turbulence
Dynamical Ensemble Equivalence between hydrodynamic dissipative equations and
suitable time-reversible dynamical systems has been investigated in a class of
dynamical systems for turbulence. The reversible dynamics is obtained from the
original dissipative equations by imposing a global constraint. We find that,
by increasing the input energy, the system changes from an equilibrium state to
a non-equilibrium stationary state in which an energy cascade, with the same
statistical properties of the original system, is clearly detected.Comment: 16 pages Latex, 4 PS figures, on press on J. Phy
Evidence for an incommensurate magnetic resonance in La(2-x)Sr(x)CuO(4)
We study the effect of a magnetic field (applied along the c-axis) on the
low-energy, incommensurate magnetic fluctuations in superconducting
La(1.82)Sr(0.18)CuO(4). The incommensurate peaks at 9 meV, which in zero-field
were previously shown to sharpen in q on cooling below T_c [T. E. Mason et al.,
Phys. Rev. Lett. 77, 1604 (1996)], are found to broaden in q when a field of 10
T is applied. The applied field also causes scattered intensity to shift into
the spin gap. We point out that the response at 9 meV, though occurring at
incommensurate wave vectors, is comparable to the commensurate magnetic
resonance observed at higher energies in other cuprate superconductors.Comment: 8 pages, including 4 figure
Experimental study of ion heating and acceleration during magnetic reconnection
Ion heating and acceleration has been studied in the well-characterized reconnection layer of the Magnetic Reconnection Experiment [M. Yamada , Phys. Plasmas 4, 1936 (1997)]. Ion temperature in the layer rises substantially during null-helicity reconnection in which reconnecting field lines are anti-parallel. The plasma outflow is sub-Alfvenic due to a downstream back pressure. An ion energy balance calculation based on the data and including classical viscous heating indicates that ions are heated largely via nonclassical mechanisms. The T-i rise is much smaller during co-helicity reconnection in which field lines reconnect obliquely. This is consistent with a slower reconnection rate and a smaller resistivity enhancement over the Spitzer value. These observations show that nonclassical dissipation mechanisms can play an important role both in heating the ions and in facilitating the reconnection process
Nearly Instantaneous Alternatives in Quantum Mechanics
Usual quantum mechanics predicts probabilities for the outcomes of
measurements carried out at definite moments of time. However, realistic
measurements do not take place in an instant, but are extended over a period of
time. The assumption of instantaneous alternatives in usual quantum mechanics
is an approximation whose validity can be investigated in the generalized
quantum mechanics of closed systems in which probabilities are predicted for
spacetime alternatives that extend over time. In this paper we investigate how
alternatives extended over time reduce to the usual instantaneous alternatives
in a simple model in non-relativistic quantum mechanics. Specifically, we show
how the decoherence of a particular set of spacetime alternatives becomes
automatic as the time over which they extend approaches zero and estimate how
large this time can be before the interference between the alternatives becomes
non-negligible. These results suggest that the time scale over which coarse
grainings of such quantities as the center of mass position of a massive body
may be extended in time before producing significant interference is much
longer than characteristic dynamical time scales.Comment: 12 pages, harvmac, no figure
Similar glassy features in the NMR response of pure and disordered La1.88Sr0.12CuO4
High Tc superconductivity in La2-xSrxCuO4 coexists with (striped and glassy)
magnetic order. Here, we report NMR measurements of the 139La spin-lattice
relaxation, which displays a stretched-exponential time dependence, in both
pure and disordered x=0.12 single crystals. An analysis in terms of a
distribution of relaxation rates T1^-1 indicates that i) the spin-freezing
temperature is spatially inhomogeneous with an onset at Tg(onset)=20 K for the
pristine samples, and ii) the width of the T1^-1 distribution in the vicinity
of Tg(onset) is insensitive to an ~1% level of atomic disorder in CuO2 planes.
This suggests that the stretched-exponential 139La relaxation, considered as a
manifestation of the systems glassiness, may not arise from quenched disorder.Comment: 7 pages, to be published in Phys. Rev.
Entanglement of an impurity and conduction spins in the Kondo model
Based on Yosida's ground state of the single-impurity Kondo Hamiltonian, we
study three kinds of entanglement between an impurity and conduction electron
spins. First, it is shown that the impurity spin is maximally entangled with
all the conduction electrons. Second, a two-spin density matrix of the impurity
spin and one conduction electron spin is given by a Werner state. We find that
the impurity spin is not entangled with one conduction electron spin even
within the Kondo screening length , although there is the spin-spin
correlation between them. Third, we show the density matrix of two conduction
electron spins is nearly same to that of a free electron gas. The single
impurity does not change the entanglement structure of the conduction electrons
in contrast to the dramatic change in electrical resistance.Comment: 5 pages, 2 figures, accepted for publication in Physical Review
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