50 research outputs found
Does dark matter consist of baryons of new stable family quarks?
We investigate the possibility that the dark matter consists of clusters of
the heavy family quarks and leptons with zero Yukawa couplings to the lower
families. Such a family is predicted by the {\it approach unifying spin and
charges} as the fifth family. We make a rough estimation of properties of
baryons of this new family members, of their behaviour during the evolution of
the universe and when scattering on the ordinary matter and study possible
limitations on the family properties due to the cosmological and direct
experimental evidences.Comment: 28 pages, revtex, submitted to Phys. Rev. Let
"An effective two dimensionality" cases bring a new hope to the Kaluza-Klein[like] theories
One step towards realistic Kaluza-Klein[like] theories and a loop hole
through the Witten's "no-go theorem" is presented for cases which we call an
effective two dimensionality cases: In the equations of motion following
from the action with the linear curvature leave spin connections and zweibeins
undetermined. We present the case of a spinor in compactified on a
formally infinite disc with the zweibein which makes a disc curved on an almost
and with the spin connection field which allows on such a sphere only one
massless normalizable spinor state of a particular charge, which couples the
spinor chirally to the corresponding Kaluza-Klein gauge field. We assume no
external gauge fields. The masslessness of a spinor is achieved by the choice
of a spin connection field (which breaks parity), the zweibein and the
normalizability condition for spinor states, which guarantee a discrete
spectrum forming the complete basis. We discuss the meaning of the hole, which
manifests the noncompactness of the space.Comment: 26 pages, 1 figure, an addition which helps to clarify the
assumptions and their consequences (the discreteness of spectrum, the
massless solution of one handedness,..
On the origin of families of quarks and leptons - predictions for four families
The approach unifying all the internal degrees of freedom--proposed by one of
us--is offering a new way of understanding families of quarks and leptons: A
part of the starting Lagrange density in d(=1+13), which includes two kinds of
spin connection fields--the gauge fields of two types of Clifford algebra
objects--transforms the right handed quarks and leptons into the left handed
ones manifesting in d=1+3 the Yukawa couplings of the Standard model. We study
the influence of the way of breaking symmetries on the Yukawa couplings and
estimate properties of the fourth family--the quark masses and the mixing
matrix, investigating the possibility that the fourth family of quarks and
leptons appears at low enough energies to be observable with the new generation
of accelerators.Comment: 31 pages,revte
Puzzles of Dark Matter - More Light on Dark Atoms?
Positive results of dark matter searches in experiments DAMA/NaI and
DAMA/LIBRA confronted with results of other groups can imply nontrivial
particle physics solutions for cosmological dark matter. Stable particles with
charge -2, bound with primordial helium in O-helium "atoms" (OHe), represent a
specific nuclear-interacting form of dark matter. Slowed down in the
terrestrial matter, OHe is elusive for direct methods of underground Dark
matter detection using its nuclear recoil. However, low energy binding of OHe
with sodium nuclei can lead to annual variations of energy release from OHe
radiative capture in the interval of energy 2-4 keV in DAMA/NaI and DAMA/LIBRA
experiments. At nuclear parameters, reproducing DAMA results, the energy
release predicted for detectors with chemical content other than NaI differ in
the most cases from the one in DAMA detector. Moreover there is no bound
systems of OHe with light and heavy nuclei, so that there is no radiative
capture of OHe in detectors with xenon or helium content. Due to dipole Coulomb
barrier, transitions to more energetic levels of Na+OHe system with much higher
energy release are suppressed in the correspondence with the results of DAMA
experiments. The proposed explanation inevitably leads to prediction of
abundance of anomalous Na, corresponding to the signal, observed by DAMA.Comment: Contribution to Proceedings of XIII Bled Workshop "What Comes beyond
the Standard Model?
Enhanced Microwave Absorption Properties of Intrinsically Core/shell Structured La0.6Sr0.4MnO3Nanoparticles
The intrinsically core/shell structured La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores have been prepared. The magnetic, dielectric and microwave absorption properties are investigated in the frequency range from 1 to 12 GHz. An optimal reflection loss of −41.1 dB is reached at 8.2 GHz with a matching thickness of 2.2 mm, the bandwidth with a reflection loss less than −10 dB is obtained in the 5.5–11.3 GHz range for absorber thicknesses of 1.5–2.5 mm. The excellent microwave absorption properties are a consequence of the better electromagnetic matching due to the existence of the protective amorphous shells, the ferromagnetic cores, as well as the particular core/shell microstructure. As a result, the La0.6Sr0.4MnO3nanoparticles with amorphous shells and ferromagnetic cores may become attractive candidates for the new types of electromagnetic wave absorption materials