2,904 research outputs found
The Absorptive Extra Dimensions
It is well known that gravity and neutrino oscillation can be used to probe
large extra dimensions in a braneworld scenario. We argue that neutrino
oscillation remains a useful probe even when the extra dimensions are small,
because the brane-bulk coupling is likely to be large. Neutrino oscillation in
the presence of a strong brane-bulk coupling is vastly different from the usual
case of a weak coupling. In particular, some active neutrinos could be absorbed
by the bulk when they oscillate from one kind to another, a signature which can
be taken as the presence of an extra dimension. In a very large class of models
which we shall discuss, the amount of absorption for all neutrino oscillations
is controlled by a single parameter, a property which distinguishes extra
dimensions from other mechanisms for losing neutrino fluxes.Comment: Introduction enlarged; conclusions added. To appear in Phys. Rev.
Sterile Neutrino as a Bulk Neutrino
If light sterile neutrinos are needed to understand the neutrino puzzles, as
is currently indicated, a major theoretical challenge is to understand why its
mass is so small. It is a more serious problem than understanding the small
mass of the familiar neutrinos. We discuss a new way to solve this problem by
identifying the sterile neutrino as gauge neutral fermion propagating in the
bulk of a higher dimensional theory, with bulk size of order of a millimeter.
The smallness of its mass is then a consequence of the size of the extra
dimension and does not need the introduction of new symmetries. We present a
realistic model for neutrino masses and mixings that implements this idea.Comment: 13 pages, no figures; minor typos correcte
Effect of Plastic Deformation on the Magnetic Properties 304 Stainless Steel During Tensile Loading
The present investigation addresses effect of tensile deformation on the magnetic properties of virgin 304SS as well as cold rolled samples containing a low
volume fraction of 12% and 17% martensite. In-situ Non-destructive evaluation (NDE) techniques by magnetic Barkhausen emission (MBE) and magnetic
hysteresis loop (MHL) measurement were used for evaluation of plastic deformation during tensile loading. Both the techniques indicated different stages of variation in
magnetic properties with progressive plastic deformation. The trend of coercivity and Barkhausen measurements also throw light on the ductile and brittle fracture occurring in virgin and cold worked samples with validation using SEM
fractography
Naturally Small Seesaw Neutrino Mass with No New Physics Beyond the TeV Scale
If there is no new physics beyond the TeV energy scale, such as in a theory
of large extra dimensions, the smallness of the seesaw neutrino mass, i.e.
, cannot be explained by a very large . In contrast to
previous attempts to find an alternative mechanism for a small , I show
how a solution may be obtained in a simple extension of the Standard Model,
without using any ingredient supplied by the large extra dimensions. It is also
experimentally testable at future accelerators.Comment: 9 pages, in final form for PR
Magnetic behavior of nanocrystalline ErCo2
We have investigated the magnetic behavior of the nanocrystalline form of a
well-known Laves phase compound, ErCo2 - the bulk form of which has been known
to undergo an interesting first-order ferrimagnetic ordering near 32 K -
synthesized by high-energy ball-milling. It is found that, in these
nanocrystallites, Co exhibits ferromagnetic order at room temperature as
inferred from the magnetization data. However, the magnetic transition
temperature for Er sublattice remains essentially unaffected as though the
(Er)4f-Co(3d) coupling is weak on Er magnetism. The net magnetic moment as
measured at high fields, sat at 120 kOe, is significantly reduced with respect
to that for the bulk in the ferrimagnetically ordered state and possible
reasons are outlined. We have also compared the magnetocaloric behavior for the
bulk and the nano particles.Comment: JPCM, in pres
Possible Z-width probe of a "brane-world" scenario for neutrino masses
The possibility that the accurately known value of the Z width might furnish
information about the coupling of two neutrinos to the Majoron (Nambu-Goldstone
boson of spontaneous lepton number violation) is proposed and investigated in
detail. Both the "ordinary" case and the case in which one adopts a "brane"
world picture with the Majoron free to travel in extra dimensions are studied.
Bounds on the dimensionless coupling constants are obtained, allowing for any
number of extra dimensions and any intrinsic mass scale. These bounds may be
applied to a variety of different Majoron models. If a technically natural
see-saw model is adopted, the predicted coupling constants are far below these
upper bounds. In addition, for this natural model, the effect of extra
dimensions is to decrease the predicted partial Z width, the increase due to
many Kaluza-Klein excitations being compensated by the decrease of their common
coupling constant.Comment: RevTeX, 12 pages, 3 figure
Neutrino Oscillations via the Bulk
We investigate the possibility that the large mixing of neutrinos is induced
by their large coupling to a five-dimensional bulk neutrino. In the strong
coupling limit the model is exactly soluble. It gives rise to an oscillation
amplitude whose squared-mass difference is independent of the channel, thus
making it impossible to explain both the solar and the atmospheric neutrino
oscillations simultaneously.Comment: References added and rearranged, typos corrected, a graph added, and
more detailed explanations provided. To appear in Physical Review
Magnetic behavior of nano crystals of a spin-chain system, Ca3Co2O6: Absence of multiple steps in the low temperature isothermal magnetization
We report that the major features in the temperature dependence of dc and ac
magnetization of a well-known spin-chain compound, Ca3Co2O6, which has been
known to exhibit two complex magnetic transitions due to geometrical
frustration (one near 24 K and the other near 10 K), are found to be
qualitatively unaffected in its nano form synthesized by high-energy
ball-milling. However, the multiple steps in isothermal magnetization - a topic
of current interest in low-dimensional systems - known for the bulk form well
below 10 K is absent in the nano particles. We believe that this finding will
be useful to the understanding of the 'step' magnetization behavior of such
spin-chain systems.Comment: Phys. Rev. B (Rapid Communications), in pres
Minimal SUSY SO(10) model and predictions for neutrino mixings and leptonic CP violation
We discuss a minimal Supersymmetric SO(10) model where B-L symmetry is broken
by a {\bf 126} dimensional Higgs multiplet which also contributes to fermion
masses in conjunction with a {\bf 10} dimensional superfield. This minimal
Higgs choice provides a partial unification of neutrino flavor structure with
that of quarks and has been shown to predict all three neutrino mixing angles
and the solar mass splitting in agreement with observations, provided one uses
the type II seesaw formula for neutrino masses. In this paper we generalize
this analysis to include arbitrary CP phases in couplings and vevs. We find
that (i) the predictions for neutrino mixings are similar with as before and other parameters in a somewhat bigger range and (ii) that
to first order in the quark mixing parameter (the Cabibbo angle), the
leptonic mixing matrix is CP conserving. We also find that in the absence of
any higher dimensional contributions to fermion masses, the CKM phase is
different from that of the standard model implying that there must be new
contributions to quark CP violation from the supersymmetry breaking sector.
Inclusion of higher dimensional terms however allows the standard model CKM
phase to be maintained.Comment: 22 pages, 6 figure
Baryogenesis via Leptogenesis in presence of cosmic strings
We study the effect on leptogenesis due to cosmic strings of a
extension of the Standard Model. The disappearance of closed loops
of cosmic strings can produce heavy right handed neutrinos, 's,
whose CP-asymmetric decay in out-of-thermal equilibrium condition can give rise
to a net lepton () asymmetry which is then converted, due to sphaleron
transitions, to a Baryon () asymmetry. This is studied by using the relevant
Boltzmann equations and including the effects of both thermal and string
generated non-thermal 's. We explore the parameter region spanned by the
effective light neutrino mass parameter , the mass of the
lightest of the heavy right-handed neutrinos (or equivalently the Yukawa
coupling ) and the scale of symmetry breaking, , and
show that there exist ranges of values of these parameters, in particular with
\eta_{B-L} > 10^{11}\gev and h_1\gsim 0.01, for which the cosmic string
generated non-thermal 's can give the dominant contribution to, and indeed
produce, the observed Baryon Asymmetry of the Universe when the purely thermal
leptogenesis mechanism is not sufficient. We also discuss how, depending on the
values of , and , our results lead to upper
bounds on , where is the the CP violating phase that
determines the CP asymmetry in the decay of the heavy right handed neutrino
responsible for generating the -asymmetry.Comment: 23 pages, 5 figures, discussions added, journal version, to appear in
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