arXiv subjects

Nikodem J. Poplawski

Publications and source records attributed to Nikodem J. Poplawski.

47 records · Page 3Linked to original sources

arXiv2006

Propagating torsion in the Einstein frame

The Einstein-Cartan-Saa theory of torsion modifies the spacetime volume element so that it is compatible with the connection. The condition of connection compatibility gives constraints on torsion, which are also necessary for the consistence of torsion, minimal coupling, and electromagnetic gauge invariance. To solve the problem of positivity of energy associated with the torsionic scalar, we reformulate this theory in the Einstein conformal frame. In the presence of the electromagnetic field, we obtain the Hojman-Rosenbaum-Ryan-Shepley theory of propagating torsion with a different factor in the torsionic kinetic term.

gr-qc↗

arXiv2006

A Lagrangian description of interacting dark energy

We propose a relativistically covariant model of interacting dark energy based on the principle of least action. The cosmological term $Λ$ in the gravitational Lagrangian is a function of the trace of the energy--momentum tensor $T$. We find that the $Λ(T)$ gravity is more general than the Palatini $f(R)$ gravity, and reduces to the latter if we neglect the pressure of matter. We show that recent cosmological data favor a variable cosmological constant and are consistent with the $Λ(T)$ gravity, without knowing the specific function $Λ(T)$.

gr-qc↗

arXiv2006

Gauge invariance and massive torsionic scalar field

The Hojman-Rosenbaum-Ryan-Shepley dynamical theory of torsion preserves local gauge invariance of electrodynamics and makes minimal coupling compatible with torsion. It also allows propagation of torsion in vacuum. It is known that implications of this model disagree with the Eotvos-Dicke-Braginsky solar tests of the principle of equivalence. We modify this theory and make it consistent with experiment by introducing a massive component of the torsionic potential.

gr-qc↗

arXiv2006

The cosmic jerk parameter in f(R) gravity

We derive the expression for the jerk parameter in $f(R)$ gravity. We use the Palatini variational principle and the field equations in the Einstein conformal gauge. For the particular case $f(R)=R-\frac{α^2}{3R}$, the predicted value of the jerk parameter agrees with the SNLS SNIa and X-ray galaxy cluster distance data but does not with the SNIa gold sample data.

gr-qc↗

arXiv2006

A Michelson interferometer in the field of a plane gravitational wave

We treat the problem of a Michelson interferometer in the field of a plane gravitational wave in the framework of general relativity. The arms of the interferometer are regarded as the world lines of the light beams, whose motion is determined by the Hamilton-Jacobi equation for a massless particle. In the case of a weak monochromatic wave we find that the formula for the delay of a light beam agrees with the result obtained by solving the linearized coupled Einstein-Maxwell equations. We also calculate this delay in the next (quadratic) approximation.

gr-qc↗

arXiv2006

The present universe in the Einstein frame, metric-affine R+1/R gravity

We study the present, flat isotropic universe in 1/R-modified gravity. We use the Palatini (metric-affine) variational principle and the Einstein (metric-compatible connected) conformal frame. We show that the energy density scaling deviates from the usual scaling for nonrelativistic matter, and the largest deviation occurs in the present epoch. We find that the current deceleration parameter derived from the apparent matter density parameter is consistent with observations. There is also a small overlap between the predicted and observed values for the redshift derivative of the deceleration parameter. The predicted redshift of the deceleration-to-acceleration transition agrees with that in the Λ-CDM model but it is larger than the value estimated from SNIa observations.

gr-qc↗

arXiv2006

Acceleration of the universe in the Einstein frame of a metric-affine f(R) gravity

We show that inflation and current cosmic acceleration can be generated by a metric-affine f(R) gravity formulated in the Einstein conformal frame, if the gravitational Lagrangian L(R) contains both positive and negative powers of the curvature scalar R. In this frame, we give the equations for the expansion of the homogeneous and isotropic matter-dominated universe in the case L(R)=R+{R^3}/{β^2}-{α^2}/{3R}, where αand βare constants. We also show that gravitational effects of matter in such a universe at very late stages of its expansion are weakened by a factor that tends to 3/4, and the energy density of matter εscales the same way as in the Λ-CDM model only when κ*ε<<α.

gr-qc↗

arXiv2005

A Relativistic Description of Hadronic Decays of the Exotic Meson $π_{1}$

Exotic mesons are striking predictions of quantum chromodynamics that go beyond the quark model. They can provide great insight into understanding phenomena such as asymptotic freedom, confinement, and dynamical symmetry breaking. This work analyzes hadronic decays of exotic mesons, with a focus on the lightest one, the $J^{PC}=1^{-+}$ $π_{1}$, in a fully relativistic formalism. The relativistic spin wave functions of normal and exotic mesons are constructed based on unitary representations of the Poincare group. The radial wave functions are obtained from phenomenological considerations of the mass operator. We find that fully relativistic results using Wigner rotations differ significantly from nonrelativistic ones. Moreover, the S+P selection rule is also satisfied in relativistic formalism. Final state interactions do not change these results much.

hep-ph↗

arXiv2005

A Relativistic Description of Hadronic Decays of the Meson $π_{1}$

The subject of this work is the analysis of hadronic decays of the exotic meson $π_{1}$ in a fully relativistic formalism, and comparison with the nonrelativistic results. The relativistic spin wave functions of mesons and hybrids are constructed based on unitary representations of the Lorentz group. The radial wave functions are obtained from phenomenological considerations of the mass operator. We find that the decay channels $πb_{1}$ and $πf_{1}$ are favored, in agreement with the results obtained using other models, thus indicating some model independence of the S+P selection rules.

hep-ph↗

arXiv2005

Final State Interactions in Decays of the Exotic $π_{1}$ Meson

We analyze the role of final state interactions in decay of the lighest exotic meson, $pi_1$ with $J^{PC}=1^{-+}. We use the relativistic Lippmann-Schwinger equation for two coupled $πb_{1}$ and $πρ$ channels. The first one is the predicted dominant decay mode of the $π_{1}$, whereas in the other a narrow $π_1(1600)$ exotic signal has been reported by the E852 collaboration. The FSI potential is constructed, based on the $ω$ meson exchange between the two channels. We find that this process introduces corrections to the $π_{1}$ widths of the order of only a few MeV. Therefore, we conclude that a substantial $πρ$ mode cannot be generated through level mixing.

hep-ph↗

arXiv2004

Towards a Relativistic Description of Exotic Meson Decays

This work analyses hadronic decays of exotic mesons, with a focus on the lightest one, the $J^{PC}=1^{-+}$ $π_{1}$, in a fully relativistic formalism, and makes comparisons with non-relativistic results. We also discuss Coulomb gauge decays of normal mesons that proceed through their hybrid components. The relativistic spin wave functions of mesons and hybrids are constructed based on unitary representations of the Lorentz group. The radial wave functions are obtained from phenomenological considerations of the mass operator. Fully relativistic results (with Wigner rotations) differ significantly from non-relativistic ones. We also find that the decay channels $π_{1}\toπb_{1}, πf_{1}, KK_{1}$ are favored, in agreement with results obtained using other models.

hep-ph↗