2,259,754 research outputs found
Aspects of Neutrino Mass Matrices
After an Introduction briefly describing the rise and fall of the three-zero
texture of the Zee model, we discuss still-allowed two-zero textures for the
Majorana three-neutrino mass matrix. Finally, a model with two right-handed
neutrinos and two Dirac texture zeros is described (FGY model) which can relate
CP violation in leptogenesis to CP violation in long-baseline neutrino
oscillations.Comment: 9 pages latex. Talk at Coral Gables 2003. Added reference
Structure for the breathing mode of the nucleon from high energy p-p scattering
Spectra of p-p and pi-p scattering at beam momenta between 6 and 30 GeV/c
have been reanalysed. These show strong excitation of N* resonances, the
strongest one corresponding to the "scalar" P11 excitation (breathing mode) at
m_o= 1400+-10 MeV with Gamma= 200+-25 MeV. The result of a strong scalar
excitation is supported by a large longitudinal amplitude S_1/2 extracted from
e-p scattering. From exclusive data on p+p=>p p pi+ pi- a large 2pi-N decay
branch for the P_11 resonance of B_2pi= 75+-20 % has been extracted.
The differential cross sections were described in a double folding approach,
assuming multi-gluon exchange as the dominant part of the effective interaction
between the constituents of projectile and target. First, the parameters of the
interaction were fitted to elastic scattering; then with this interaction the
inelastic cross sections were described in the distorted wave Born
approximation. A good description of the data requires a surface peaked
transition density, quite different from that of a pure radial mode. In
contrast, the electron scattering amplitude S_1/2 is quite well described by a
breathing mode transition density with radial node. This large difference
between charge and matter transition density suggests, that in p-p scattering
the coupling to the multi-gluon field is much more important than the coupling
to the valence quarks. A multi-gluon (or sea-quark) transition density is
derived, which shows also breathing, indicating a rather complex multi-quark
structure of N and N* including multi-glue (or q^2n qbar ^-2n) creation out of
the g.s. vacuum.Comment: 18 pages with 7 figure
Quantum Bit Commitment with a Composite Evidence
Entanglement-based attacks, which are subtle and powerful, are usually
believed to render quantum bit commitment insecure. We point out that the no-go
argument leading to this view implicitly assumes the evidence-of-commitment to
be a monolithic quantum system. We argue that more general evidence structures,
allowing for a composite, hybrid (classical-quantum) evidence, conduce to
improved security. In particular, we present and prove the security of the
following protocol: Bob sends Alice an anonymous state. She inscribes her
commitment by measuring part of it in the + (for ) or (for
) basis. She then communicates to him the (classical) measurement outcome
and the part-measured anonymous state interpolated into other, randomly
prepared qubits as her evidence-of-commitment.Comment: 6 pages, minor changes, journal reference adde
A Monte Carlo study of critical properties of strongly diluted magnetic semiconductor (Ga,Mn)As
Within a Monte Carlo technique we examine critical properties of diluted bulk
magnetic semiconductor (Ga,Mn)As modeled by a strongly diluted ferromagnetic
Heisenberg spin- system on a face centered cubic lattice. We
assumed that 5\% of Ga atoms is substituted by Mn atoms and the interaction
between them is of the RKKY-type. The considered system is randomly quenched
and a double average was performed: firstly, over the Boltzmann probability
distribution and secondly - over 2048 configurations related to the quenched
disorder. We estimated the critical temperature: K, which is in
agreement with the experiment. The calculated high value of critical exponent
seems to point to a possibility of non-universal critical behavior.Comment: 4 pages, 6 figure
Superdeformed Bands of Odd Nuclei in A=190 Region in the Quasiparticle Picture
We study the properties of the superdeformed (SD) bands of 195Pb and 193Hg by
the cranked Hartree-Fock-Bogoliubov method. Our calculations reproduce the flat
behavior of the dynamical moment of inertia of two of the SD bands of 195Pb
measured recently. We discuss possible configuration assignments for the
observed bands 3 and 4 of 195Pb. We also calculate the two interacting SD bands
of 193Hg. Our analysis confirms the superiority of a density-dependent pairing
force over a seniority pairing interaction.Comment: 12 pages, 5 Postscript figures, submitted to Phys.Rev.
Finite Volume Scaling of Pseudo Nambu-Goldstone Bosons in QCD
We consider chiral perturbation theory in a finite volume and in a mixed
regime of quark masses. We take N_l light quarks near the chiral limit, in the
so-called epsilon-regime, while the remaining N_h quarks are heavier and in the
standard p-regime. We compute in this new mixed regime the finite-size scaling
of the light meson correlators in the scalar, pseudoscalar, vector and axial
vector channels.Using the replica method, we easily extend our results to the
partially quenched theory. With the help of our results, lattice QCD
simulations with 2+1 flavors can safely investigate pion physics with very
light up and down quark masses even in the region where the pion's correlation
length overcomes the size of the space-time lattice.Comment: 32 pages, 6 figures, published versio
Electro-Coalescence Fireworks
Electro-coalescence is the application of an electric field onto coalescing
fluid bodies. The following fluid dynamics videos show a droplet coalescing
into a fluid bath while embedded into a viscous medium and subject to a very
high electric field. The concentration of electric stresses at the apex of the
droplet cause it to break apart. The droplet is glycerol and the viscous medium
is silicone oil
Low energy threshold corrections to neutrino masses and mixing angles
We compute the low energy threshold corrections to neutrino masses and mixing
in the Standard Model (SM) and its minimal supersymmetric version, using the
effective theory technique. We demonstrate that they stabilize the
renormalization group (RG) running with respect to the choice of the scale to
which the RG equation is integrated. This confirms the correctness of the
recent re-derivation of the RGE for the SM in hep-ph/0108005. The explicit
formulae for the low energy threshold corrections corrections can be applied to
specific models of neutrino masses and mixing.Comment: 20 pages, 2 postscript figure
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