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B. Kleihaus

Publications and source records attributed to B. Kleihaus.

At least 19 recordsLinked to original sources
arXiv2022

Horndeski Proca stars with vector hair

We study Proca stars in a vector-tensor gravity model inspired by Horndeski's generalized Einstein-Maxwell field equations, supplemented with a mass term for the vector field. We discuss the effects of the non-minimal coupling term on the properties of the resulting Proca stars. %and show that they can form vector hair. We show that the sign of the coupling constant is crucial in determining the generic properties of these generalized Proca star solutions, as soon as the magnitude of the coupling constant is sufficiently large to allow for significant deviations from the standard Proca star case. For negative coupling constant we observe a new type of limiting behavior for the generalized Proca stars, where the spacetime splits into an interior region with matter fields and an exterior Schwarzschild region.

gr-qc↗
arXiv2013

Quantum torsion with non-zero standard deviation: non-perturbative approach for cosmology

Cosmology with non-perturbative quantum corrections resulting from torsion is considered. It is shown that the evolution of closed, open and flat Universes is changed because of the presence of a non-zero dispersion of quantum torsion. The evolution of a Universe with quantum torsion and with one type of average curvature can be similar to the evolution of a Universe without quantum torsion and with another type of average curvature. For the description of the non-perturbative quantum torsion, a vector field approximation is applied.

gr-qc↗
arXiv2011

A Star Harbouring a Wormhole at its Core

We consider a configuration consisting of a wormhole filled by a perfect fluid. Such a model can be applied to describe stars as well as neutron stars with a nontrivial topology. The presence of a tunnel allows for motion of the fluid, including oscillations near the core of the system. Choosing the polytropic equation of state for the perfect fluid, we obtain static regular solutions. Based on these solutions, we consider small radial oscillations of the configuration and show that the solutions are stable with respect to linear perturbations in the external region.

astro-ph.GA↗
arXiv2010

Some thick brane solutions in $f(R)$-gravity

The thick brane model is considered in $f(R)\sim R^n$ gravity. It is shown that regular asymptotically anti-de Sitter solutions exist in some range of values of the parameter $n$. A peculiar feature of this model is the existence of a fixed point in the phase plane where all solutions start, and the brane can be placed at this point. The presence of the fixed point allows to avoid fine tuning of the model parameters to obtain thick brane solutions.

gr-qc↗
arXiv2004

Rotating Black Holes with Monopole Hair

We study rotating black holes in Einstein-Yang-Mills-Higgs theory. These black holes emerge from static black holes with monopole hair when a finite horizon angular velocity is imposed. At critical values of the horizon angular velocity and the horizon radius, they bifurcate with embedded Kerr-Newman black holes. The non-Abelian black holes possess an electric dipole moment, but no electric charge is induced by the rotation. We deduce that gravitating regular monopoles possess a gyroelectric ratio g_el=2.

gr-qc↗
arXiv2003

Platonic Sphalerons

We construct sphaleron solutions in Weinberg-Salam theory, which possess only discrete symmetries. Related to rational maps of degree N, these sphalerons carry baryon number Q_B=N/2. The energy density of these sphalerons reflects their discrete symmetries. We present an N=3 sphaleron with tetrahedral energy density, an N=4 sphaleron with cubic energy density, and an N=5 sphaleron with octahedral energy density.

hep-th↗
arXiv2003

Monopoles, Antimonopoles and Vortex Rings

We present a new class of static axially symmetric solutions of SU(2) Yang-Mills-Higgs theory, where the Higgs field vanishes on rings centered around the symmetry axis. Associating a magnetic dipole moment with each Higgs vortex ring, the dipole moments add for solutions in the trivial topological sector, whereas they cancel for magnetically charged solutions.

hep-th↗
arXiv2003

Monopole--Antimonopole Chains

We present new static axially symmetric solutions of SU(2) Yang-Mills-Higgs theory, representing chains of monopoles and antimonopoles in static equilibrium. They correspond to saddlepoints of the energy functional and exist both in the topologically trivial sector and in the sector with topological charge one.

hep-th↗
arXiv2003

Rotating Dilaton Black Holes with Hair

We consider stationary rotating black holes in SU(2) Einstein-Yang-Mills theory, coupled to a dilaton. The black holes possess non-trivial non-Abelian electric and magnetic fields outside their regular event horizon. While generic solutions carry no non-Abelian magnetic charge, but non-Abelian electric charge, the presence of the dilaton field allows also for rotating solutions with no non-Abelian charge at all. As a consequence, these special solutions do not exhibit the generic asymptotic non-integer power fall-off of the non-Abelian gauge field functions. The rotating black hole solutions form sequences, characterized by the winding number $n$ and the node number $k$ of their gauge field functions, tending to embedded Abelian black holes. The stationary non-Abelian black hole solutions satisfy a mass formula, similar to the Smarr formula, where the dilaton charge enters instead of the magnetic charge. Introducing a topological charge, we conjecture, that black hole solutions in SU(2) Einstein-Yang-Mills-dilaton theory are uniquely characterized by their mass, their angular momentum, their dilaton charge, their non-Abelian electric charge, and their topological charge.

gr-qc↗
arXiv2002

Global Charges of Stationary Non-Abelian Black Holes

We consider stationary axially symmetric black holes in SU(2) Einstein-Yang-Mills-dilaton theory. We present a mass formula for these stationary non-Abelian black holes, which also holds for Abelian black holes. The presence of the dilaton field allows for rotating black holes, which possess non-trivial electric and magnetic gauge fields, but don't carry a non-Abelian charge.

hep-th↗
arXiv2002

Rotating Einstein-Yang-Mills Black Holes

We construct rotating hairy black holes in SU(2) Einstein-Yang-Mills theory. These stationary axially symmetric black holes are asymptotically flat. They possess non-trivial non-Abelian gauge fields outside their regular event horizon, and they carry non-Abelian electric charge. In the limit of vanishing angular momentum, they emerge from the neutral static spherically symmetric Einstein-Yang-Mills black holes, labelled by the node number of the gauge field function. With increasing angular momentum and mass, the non-Abelian electric charge of the solutions increases, but remains finite. The asymptotic expansion for these black hole solutions includes non-integer powers of the radial variable.

gr-qc↗
arXiv2001

Horizon Properties of Einstein-Yang-Mills Black Hole

We consider static axially symmetric Einstein-Yang-Mills black holes in the isolated horizon formalism. The mass of these hairy black holes is related to the mass of the corresponding particle-like solutions by the horizon mass. The hairy black holes violate the ``quasi-local uniqueness conjecture'', based on the horizon charges.

gr-qc↗
arXiv2000

Rotating Hairy Black Holes

We construct stationary black holes in SU(2) Einstein-Yang-Mills theory, which carry angular momentum and electric charge. Possessing non-trivial non-abelian magnetic fields outside their regular event horizon, they represent non-perturbative rotating hairy black holes.

gr-qc↗
arXiv2000

Non-Abelian Black Holes with Magnetic Dipole Hair

We construct static axially symmetric black holes in SU(2) Einstein-Yang-Mills-Higgs theory. Located in between a monopole-antimonopole pair, these black holes possess magnetic dipole hair. The difference of their mass and their horizon mass equals the mass of the regular monopole-antimonopole solution, as expected from the isolated horizon framework.

hep-th↗
arXiv1999

A Monopole-Antimonopole Solution of the SU(2) Yang-Mills-Higgs Model

As shown by Taubes, in the Bogomol'nyi-Prasad-Sommerfield limit the SU(2) Yang-Mills-Higgs model possesses smooth finite energy solutions, which do not satisfy the first order Bogomol'nyi equations. We construct numerically such a non-Bogomol'nyi solution, corresponding to a monopole-antimonopole pair, and extend the construction to finite Higgs potential.

hep-th↗