15,091 research outputs found
Highly-boosted dark matter and cutoff for cosmic-ray neutrino through neutrino portal
We study the cutoff for the cosmic-ray neutrino, set by the scattering with
cosmic background neutrinos into dark sector particles through a neutrino
portal interaction. We find that a large interaction rate is still viable, when
the dark sector particles are mainly coupled to the neutrino, so that
the neutrino mean free path can be reduced to be Mpc over a wide energy
range. If stable enough, the dark sector particle, into which most of the
cosmic-ray neutrino energy is transferred, can travel across the Universe and
reach the earth. The dark sector particle can carry the energy as large as
\O({\rm EeV}) if originates from a cosmogenic neutrino.Comment: 6 pages, 7 figures, v2: match the published versio
Charge Quantization and Neutrino Mass from Planck-scale SUSY
We show a possibility for the charge quantization of the standard model (SM)
particles. If a global symmetry makes the three copies of a generation and
supersymmetry (SUSY) relates the Higgs boson to a lepton, all the charges of
the SM particles can be quantized through gauge-anomaly cancellation. In the
minimal model realizing the possibility, the gravitino mass around the
Planck-scale is needed to generate the SM couplings through (quantum)
supergravity. Much below the Planck-scale, the SM is obtained as the effective
theory. Interestingly, if the gaugino masses are generated through anomaly
mediation, one of the neutrino masses is predicted to be around the neutrino
oscillation scales. In an extension of the model, millicharged particles can
exist without introducing massless hidden photons.Comment: 17 pages, v2: version appears in PL
Natural Split Mechanism for Sfermions: =2 Supersymmetry in Phenomenology
We suggest a natural split mechanism for sfermions based on =2
supersymmetry (SUSY). =2 SUSY protects a sfermion in an =2 multiplet from
gaining weight by SUSY breaking. Therefore, if partly =2 SUSY is effectively
obtained, a split spectrum can be realized naturally. As an example of the
natural split mechanism, we build a gauge-mediated SUSY breaking-like model
assuming =2 SUSY is partly broken in a UV theory. The model explains the
Higgs boson mass and the muon anomalous magnetic dipole moment within
level with a splitting sfermion spectrum. The model has seven light
sparticles described by three free parameters and predicts a new chiral
multiplet, sb: the =2 partner of the vector multiplet. The
bini, the fermion component of the sb, weighs MeVs. We mention the experimental
and the cosmological aspects of the model.Comment: 17 pages and 3 figures, Version accepted for publication in PL
An Alternating Direction Algorithm for Matrix Completion with Nonnegative Factors
This paper introduces an algorithm for the nonnegative matrix
factorization-and-completion problem, which aims to find nonnegative low-rank
matrices X and Y so that the product XY approximates a nonnegative data matrix
M whose elements are partially known (to a certain accuracy). This problem
aggregates two existing problems: (i) nonnegative matrix factorization where
all entries of M are given, and (ii) low-rank matrix completion where
nonnegativity is not required. By taking the advantages of both nonnegativity
and low-rankness, one can generally obtain superior results than those of just
using one of the two properties. We propose to solve the non-convex constrained
least-squares problem using an algorithm based on the classic alternating
direction augmented Lagrangian method. Preliminary convergence properties of
the algorithm and numerical simulation results are presented. Compared to a
recent algorithm for nonnegative matrix factorization, the proposed algorithm
produces factorizations of similar quality using only about half of the matrix
entries. On tasks of recovering incomplete grayscale and hyperspectral images,
the proposed algorithm yields overall better qualities than those produced by
two recent matrix-completion algorithms that do not exploit nonnegativity
- …