arXiv subjects

Nikodem J. Popławski

Publications and source records attributed to Nikodem J. Popławski.

6 recordsLinked to original sources

arXiv2026

A nonsingular, anisotropic universe in a black hole with torsion and particle production

We consider a universe formed in a black hole in general relativity with spin and torsion. The interior of a Schwarzschild black hole can be represented by the Kantowski$-$Sachs metric that describes a closed anisotropic universe. We use this metric to derive the Einstein$-$Cartan field equations with a relativistic spin fluid as a source. We show that torsion may prevent a singularity and replace it with a nonsingular bounce if particle production dominates over shear. Particle production after the last bounce can generate a finite period of inflation, during which the universe expands and isotropizes to the current state. This scenario is only approximate: the Kantowski$-$Sachs metric is never reached and should be replaced with a more general metric that tends to that of a 3-sphere.

gr-qc↗

arXiv2026

The energy and momentum of the Universe

The Einstein$-$Cartan$-$Sciama$-$Kibble theory of gravity naturally extends general relativity to include quantum-mechanical, intrinsic angular momentum of matter by equipping spacetime with torsion. Using the Einstein energy$-$momentum pseudotensor for the gravitational field in this theory, we show that the energy and momentum of the closed Universe are equal to zero. Since the positive energy from mass and motion of the observed matter in the Universe exceeds in magnitude the negative energy from gravity, the Universe must contain another form of matter whose energy is negative. This form, which cannot be composed from particles, might be the observed dark matter.

gr-qc↗

arXiv2021

Phantom dark energy from scalar$-$torsion coupling

We show that a scalar field without a kinetic term in the Lagrangian density, coupled to the covariant divergence of the torsion vector in the Einstein$-$Cartan theory of gravity, becomes kinetic in its general-relativistic equivalent formulation. The resulting kinetic term is negative: such a scalar field could be a source of phantom dark energy.

gr-qc↗

arXiv2021

Non-particle dark matter from Hubble parameter

The measurements of the Hubble parameter using the cosmic microwave background radiation appear to be inconsistent with the measurements of this parameter using Cepheid variable stars. This inconsistency may be a result of using the $Λ$CDM cosmology, which assumes pressureless dark matter, in extrapolating the data from the recombination time to the present time. We show that both measurements are consistent if dark matter satisfies an equation of state in which the pressure $p$ and the energy density $ε$ are related by $p=wε$ with a negative value of $w$. The data give $w\approx -0.01$. The negative value of $w$ indicates that dark matter would not be formed by particles, which is consistent with the lack of experimental evidence for them.

physics.gen-ph↗

arXiv2020

Black Hole Genesis and origin of cosmic acceleration

We consider a hypothesis that the closed Universe was formed on the other side of the event horizon of a black hole existing in another universe. That black hole appears in the Universe as a boundary white hole, and its rest frame in comoving coordinates is a frame of reference in which the cosmic microwave background is isotropic. We consider the Lagrangian density for the gravitational field that is proportional to the curvature scalar, and use the metric-affine variational principle in which the symmetric affine connection and the metric tensor are variables. The white hole appears in the Lagrangian through a simplest, generally covariant and linear term: the four-divergence of the four-velocity of the white hole in comoving coordinates. We show that the variation of the action with respect to the connection generates the nonmetricity, which creates a term in the Lagrangian that is equivalent to a positive cosmological constant. The current cosmic acceleration may therefore be a manifestation of the boundary of the closed Universe. We also show that the equation of motion of a test particle deviates from the geodesic equation by a term that depends on the four-velocities of the particle and the white hole. The rest frame of the white hole in comoving coordinates is the only absolutely inertial frame of reference. This deviation might be observed on galactic scales.

gr-qc↗

arXiv2019

Analysis of big bounce in Einstein--Cartan cosmology

We analyze the dynamics of a homogeneous and isotropic universe in the Einstein--Cartan theory of gravity. The spin of fermions produces spacetime torsion that prevents gravitational singularities and replaces the big bang with a nonsingular big bounce. We show that a closed universe exists only when a particular function of its scale factor and temperature is higher than some threshold value, whereas an open and a flat universes do not have such a restriction. We also show that a bounce of the scale factor is double: as the temperature increases and then decreases, the scale factor decreases, increases, decreases, and then increases.

gr-qc↗