12 research outputs found
Equivalence of matter-type modified gravity theories to general relativity with nonminimal matter interaction
We show that gravity models, such as , and , that modify the introduction of
the material source in the usual Einstein-Hilbert action by adding only
matter-related terms to the matter Lagrangian density are
equivalent to general relativity with nonminimal interactions. Through the
redefinition ,
these models are exactly GR, yet the usual material field and its
accompanying partner, viz., the modification field
interact nonminimally. That is,
, where
is the interaction kernel that governs the rate of energy transfer.
We focus on the particular model, the energy-momentum squared gravity, where
the usual material field brings in an accompanying energy-momentum
squared field , along with a sui generis nonminimal
interaction between them. Compared to usual phenomenological nonminimal
interaction models in the literature, EMSF gives rise to more intricate
interaction kernels having covariant formulation even with simple forms of the
function. We elaborate upon EMSF via some different aspects: a DE component
induced from the interaction of sources such as cold dark matter and
relativistic species with their accompanying EMSFs generating interacting DE-DM
models, mimicking noncanonical scalar field, etc., or a Hoyle-type creation
field generating steady-state universe models extended to fluids other than
dust and a mimicker of modified generalized Chaplygin gas. We also demonstrate
the proper calculation of second metric variation of , as
well as in models that contain scalars like and .Comment: 16 pages, no figures and table
Double-Lepton Polarization Asymmetries and Branching Ratio of the B\rar \gamma l^+ l^- transition in Universal Extra Dimension
We study the radiative dileptonic B \rar \gamma l^+ l^- transition in the
presence of a universal extra dimension in the Applequist-Cheng-Dobrescu model.
In particular, using the corresponding form factors calculated via light cone
QCD sum rules, we analyze the branching ratio and double lepton polarization
asymmetries related to this channel and compare the results with the
predictions of the standard model. We show how the results deviate from
predictions of the standard model at lower values of the compactification
factor () of extra dimension.Comment: 20 Pages and 8 Figure
B to strange tensor meson transition in a model with one universal extra dimension
We analyze the semileptonic transition in universal
extra dimension model. In particular, we present the sensitivity of related
observables such as branching ratio, polarization distribution and
forward-backward asymmetry to the compactification factor (1/R) of extra
dimension. The obtained results from extra dimension model show overall a
considerable deviation from the standard model predictions for small values of
the compactification factor. This can be considered as an indication for
existence of extra dimensions.Comment: 10 Pges, 6 Figures and 2 Table
Analysis of \Lambda_b \rar \Lambda \ell^+ \ell^- transition in SM4 using form factors from Full QCD
Using the responsible form factors calculated via full QCD, we analyze the
transition in the standard
model containing fourth generation quarks (SM4). We discuss effects of the
presence of fourth family quark on related observables like branching
ratio, forward-backward asymmetry, baryon polarization as well as double lepton
polarization asymmetries. We also compare our results with those obtained in
the SM as well as with predictions of the SM4 but using form factors calculated
within heavy quark effective theory. The obtained results on branching ratio
indicate that the transition
is more probable in full QCD comparing to the heavy quark effective theory. It
is also shown that the results on all considered observables in SM4 deviate
considerably from the SM predictions when .Comment: 22 Pages and 21 Figure
Constraint on compactification scale via recently observed baryonic channel and analysis of the transition in SM and UED scenario
We obtain a lower limit on the compactification scale of extra dimension via
comparison of the branching ratio in the baryonic decay channel recently measured by CDF collaboration and our
previous theoretical study. We also use the newly available form factors
calculated via light cone QCD sum rules in full theory to analyze the flavour
changing neutral current process of the in universal extra dimension scenario in the presence of a single extra
compact dimension. We calculate various physical quantities like branching
ratio, forward-backward asymmetry, baryon polarizations and double lepton
polarization asymmetries defining the decay channel under consideration. We
also compare the obtained predictions with those of the standard model.Comment: 32 Pages, 27 Figures and one Tabl