Publications (49)41.23 Total impact
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ABSTRACT: By applying Schwinger's variational principle to the EinsteinCartan action for the gravitational field, we derive quantum commutation relations between the metric and torsion tensors.10/2013; 89(2). 
Article: Energy and momentum of the Universe
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ABSTRACT: The EinsteinCartanSciamaKibble theory of gravity naturally extends general relativity to include quantummechanical, intrinsic angular momentum of matter by equipping spacetime with torsion. Using the Einstein energymomentum 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, may be the observed dark matter.05/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We show that the intrinsic angular momentum of matter in curved spacetime requires the metricaffine formulation of gravity, in which the antisymmetric part of the affine connection (the torsion tensor) is not constrained to be zero but is a variable in the principle of stationary action. Regarding the tetrad and spin connection (or the metric and torsion tensors) as independent variables gives the correct generalization of the conservation law for the total (orbital plus intrinsic) angular momentum to the presence of the gravitational field. The metricaffine formulation extends general relativity to the simplest theory of gravity with intrinsic spin: the EinsteinCartanSciamaKibble theory. We also show that teleparallel gravity, which constrains the connection by setting the curvature tensor to zero, is inconsistent with the conservation of the total angular momentum.03/2013;  [Show abstract] [Hide abstract]
ABSTRACT: The existence of intrinsic spin of matter requires the metricaffine formulation of gravity, in which the affine connection is not constrained to be symmetric and its antisymmetric part (torsion tensor) is a dynamical variable. We show that the cyclic identity for the curvature tensor in the metricaffine formulation forbids fermions represented by Dirac spinors to form point or string configurations. Consequently, fermionic strings contradict the gravitational field equations in the presence of spin. Superstring theory is therefore incorrect.09/2012; 
Article: Affine theory of gravitation
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ABSTRACT: We propose a new theory of gravitation, in which the affine connection is the only dynamical variable describing the gravitational field. We construct the simplest dynamical Lagrangian density that is entirely composed from the connection, via its curvature and torsion, and is an algebraic function of its derivatives. It is given by the contraction of the Ricci tensor with a tensor which is inverse to the symmetric, contracted square of the torsion tensor, $k_{\mu\nu}=S^\rho_{\lambda\mu}S^\lambda_{\rho\nu}$. We vary the total action for the gravitational field and matter with respect to the affine connection, assuming that the matter fields couple to the connection only through $k_{\mu\nu}$. We derive the resulting field equations and show that they are identical with the Einstein equations of general relativity with a nonzero cosmological constant, if the tensor $k_{\mu\nu}$ is regarded as the metric tensor. The cosmological constant is simply a constant of proportionality between the two tensors, which together with $c$ and $G$ provides a natural system of units in gravitational physics. This theory therefore provides a physically valid construction of the metric as an algebraic function of the connection, and naturally explains dark energy as an intrinsic property of spacetime. The observed accelerating expansion of the Universe may be the strongest evidence for torsion.General Relativity and Gravitation 03/2012; · 1.90 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study cosmological perturbations arising from thermal fluctuations in the bigbounce cosmology in the EinsteinCartanSciamaKibble theory of gravity. We show that such perturbations cannot have a scaleinvariant spectrum if fermionic matter minimally coupled to the torsion tensor is macroscopically averaged as a spin fluid, but have a scaleinvariant spectrum if the Dirac form of the spin tensor of the fermionic matter is used.12/2011;  [Show abstract] [Hide abstract]
ABSTRACT: The EinsteinCartanSciamaKibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spinspin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical bigbang singularity, replacing it with a cusplike bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic.Physical review D: Particles and fields 11/2011; 85(10). 
Article: Mass of the universe in a black hole
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ABSTRACT: If spacetime torsion couples to the intrinsic spin of matter according to the EinsteinCartanSciamaKibble theory of gravity, then the resulting gravitational repulsion at supranuclear densities prevents the formation of singularities in black holes. Consequently, the interior of every black hole becomes a new universe that expands from a nonsingular bounce. We consider gravitational collapse of fermionic spinfluid matter with the stiff equation of state in a stellar black hole. Such a collapse increases the mass of the matter, which occurs through the ParkerZel'dovichStarobinskii quantum particle production in strong, anisotropic gravitational fields. The subsequent pair annihilation changes the stiff matter into an ultrarelativistic fluid. We show that the universe in a black hole of mass $M_\textrm{BH}$ at the bounce has a mass $M_\textrm{b}\sim M^2_\textrm{BH} m^{1/2}_\textrm{n}/m^{3/2}_\textrm{Pl}$, where $m_\textrm{n}$ is the mass of a neutron and $m_\textrm{Pl}$ is the reduced Planck mass. For a typical stellar black hole, $M_\textrm{b}$ is about $10^{32}$ solar masses, which is $10^6$ larger than the mass of our Universe. As the relativistic blackhole universe expands, its mass decreases until the universe becomes dominated by nonrelativistic heavy particles.10/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We derive a relation between the two polarization modes of a plane, linear gravitational wave in the secondorder approximation. Since these two polarizations are not independent, an initially monochromatic gravitational wave loses its periodic character due to the nonlinearity of the Einstein field equations. Accordingly, real gravitational waves may differ from solutions of the linearized field equations, which are being assumed in gravitationalwave detectors.09/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We consider the Lagrangian density for a free Maxwell field, in which the electromagnetic field tensor minimally couples to the affine connection, in the EinsteinCartanSciamaKibble theory of gravity. We derive the formulae for the torsion and electromagnetic field tensors in terms of the electromagnetic potential. The divergence of the magnetic field does not vanish: the photontorsion coupling acts like an effective magnetic monopole density. Such a coupling, which breaks U(1) gauge invariance, is significant only at extremely high energies existing in the very early Universe or inside black holes. It may, however, provide a mechanism for Dirac's quantization of electric charge.08/2011;  [Show abstract] [Hide abstract]
ABSTRACT: In the EinsteinCartanSciamaKibble theory of gravity, the intrinsic spin of fermionic matter generates spacetime torsion and induces gravitational repulsion at extremely high densities. This repulsion prevents the collapsing spinfluid matter in a black hole from forming a singularity. Instead, the interior of a black hole with a stiff equation of state becomes a new universe, which contracts until a (big) bounce and then expands. We derive the equations describing the dynamics of our Universe, formed in such a scenario, in terms of the conformal time which is a convenient variable for testing signatures of the contracting phase in the Cosmic Microwave Background radiation.07/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We show that the EinsteinCartanSciamaKibble theory of gravity with torsion not only extends general relativity to account for the intrinsic spin of matter, but it may also eliminate major problems in gravitational physics and answer major questions in cosmology. These problems and questions include: the origin of the Universe, the existence of singularities in black holes, the nature of inflation and dark energy, the origin of the matterantimatter asymmetry in the Universe, and the nature of dark matter.06/2011; 
Article: Big bounce from spin and torsion
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ABSTRACT: The EinsteinCartanSciamaKibble theory of gravity naturally extends general relativity to account for the intrinsic spin of matter. Spacetime torsion, generated by spin of Dirac fields, induces gravitational repulsion in fermionic matter at extremely high densities and prevents the formation of singularities. Accordingly, the big bang is replaced by a bounce that occurred when the energy density $\epsilon\propto gT^4$ was on the order of $n^2/m_\textrm{Pl}^2$ (in natural units), where $n\propto gT^3$ is the fermion number density and $g$ is the number of thermal degrees of freedom. If the early Universe contained only the known standardmodel particles ($g\approx 100$), then the energy density at the big bounce was about 15 times larger than the Planck energy. The minimum scale factor of the Universe (at the bounce) was about $10^{32}$ times smaller than its present value, giving $\approx 50 \mum$. If more fermions existed in the early Universe, then the spintorsion coupling causes a bounce at a lower energy and larger scale factor. Recent observations of highenergy photons from gammaray bursts indicate that spacetime may behave classically even at scales below the Planck length, supporting the classical spintorsion mechanism of the big bounce. Such a classical bounce prevents the matter in the contracting Universe from reaching the conditions at which a quantum bounce could possibly occur.General Relativity and Gravitation 05/2011; · 1.90 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We propose a simple mechanism that may explain the observed particleantiparticle asymmetry in the Universe. In the EinsteinCartanSciamaKibble theory of gravity, the intrinsic spin of matter generates spacetime torsion. Classical Dirac fields in the presence of torsion obey the nonlinear HehlDatta equation which is asymmetric under a chargeconjugation transformation. Accordingly, at extremely high densities that existed in the very early Universe, fermions have higher effective masses than antifermions. As a result, a meson composed of a light quark and a heavy antiquark has a lower effective mass than its antiparticle. Neutralmeson oscillations in thermal equilibrium therefore favor the production of light quarks and heavy antiquarks, which may be related to baryogenesis.04/2011;  [Show abstract] [Hide abstract]
ABSTRACT: It is shown, using the EinsteinCartanSciamaKibble theory of gravity, that gravitational collapse of spinfluid fermionic matter with a stiff equation of state in a black hole of mass $M$ forms a new universe of mass $\sim M_\ast=M^2 m_n/m_\textrm{Pl}^2$, where $m_n$ is the mass of a neutron. Equaling $M_\ast$ to the mass of the Universe, which is about $10^{26}$ solar masses, gives $M\sim 10^3$ solar masses. Our Universe may thus have originated from the interior of an intermediatemass black hole.03/2011;  [Show abstract] [Hide abstract]
ABSTRACT: We propose a simple scenario which explains the observed matterantimatter imbalance and the origin of dark matter in the Universe. We use the EinsteinCartanSciamaKibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. Spacetime torsion produced by spin generates, in the classical Dirac equation, the HehlDatta term which is cubic in spinor fields. We show that under a chargeconjugation transformation this term changes sign relative to the mass term. A classical Dirac spinor and its charge conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly to hidden antimatter which forms dark matter. The conserved total baryon number of the Universe remained zero.Physical review D: Particles and fields 01/2011; 83(8).  Developmental Biology 08/2010; 344(1):444. · 3.87 Impact Factor
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ABSTRACT: We propose a simple scenario which explains why our Universe appears spatially flat, homogeneous and isotropic. We use the EinsteinCartanKibbleSciama (ECKS) theory of gravity which naturally extends general relativity to include the spin of matter. The torsion of spacetime generates gravitational repulsion in the early Universe filled with quarks and leptons, preventing the cosmological singularity: the Universe expands from a state of minimum but finite radius. We show that the dynamics of the closed Universe immediately after this state naturally solves the flatness and horizon problems in cosmology because of an extremely small and negative torsion density parameter, $\Omega_S \approx 10^{69}$. Thus the ECKS gravity provides a compelling alternative to speculative mechanisms of standard cosmic inflation. This scenario also suggests that the contraction of our Universe preceding the bounce at the minimum radius may correspond to the dynamics of matter inside a collapsing black hole existing in another universe, which could explain the origin of the Big Bang.Physics Letters B  PHYS LETT B. 07/2010; 694.  [Show abstract] [Hide abstract]
ABSTRACT: We show that the electron in the RiemannCartan spacetime with extra dimensions has a finite size that is much larger than the experimental upper limit on its radius. Thus the ArkaniHamedDimopoulosDvali and RandallSundrum models of the weak/Planck hierarchy in particle physics are not viable if spin produces torsion according to the EinsteinCartan theory of gravity. Comment: 3 pages01/2010;  [Show abstract] [Hide abstract]
ABSTRACT: We use the GlazierGranerHogeweg model to simulate threedimensional (3D), singlephenotype, avascular tumors growing in an homogeneous tissue matrix (TM) supplying a single limiting nutrient. We study the effects of two parameters on tumor morphology: a diffusionlimitation parameter defined as the ratio of the tumorsubstrate consumption rate to the substratetransport rate, and the tumorTM surface tension. This initial model omits necrosis and oxidative/hypoxic metabolism effects, which can further influence tumor morphology, but our simplified model still shows significant parameter dependencies. The diffusionlimitation parameter determines whether the growing solid tumor develops a smooth (noninvasive) or fingered (invasive) interface, as in our earlier twodimensional (2D) simulations. The sensitivity of 3D tumor morphology to tumorTM surface tension increases with the size of the diffusionlimitation parameter, as in 2D. The 3D results are unexpectedly close to those in 2D. Our results therefore may justify using simpler 2D simulations of tumor growth, instead of more realistic but more computationally expensive 3D simulations. While geometrical artifacts mean that 2D sections of connected 3D tumors may be disconnected, the morphologies of 3D simulated tumors nevertheless correlate with the morphologies of their 2D sections, especially for lowsurfacetension tumors, allowing the use of 2D sections to partially reconstruct medicallyimportant 3Dtumor structures.PLoS ONE 01/2010; 5(5):e10641. · 3.73 Impact Factor
Publication Stats
223  Citations  
41.23  Total Impact Points  
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Institutions

2004–2011

Indiana University Bloomington
 • Department of Physics
 • Biocomplexity Institute
Bloomington, IN, United States


2010

National Cancer Institute (USA)
Maryland, United States
