198 citations · 3.3k across the 147 of their papers we have counts for
8 papers · 1 filter
Gluonic vacuum, q-theory, and the cosmological constant
F. R. Klinkhamer, G. E. Volovik
In previous work, q-theory was introduced to describe the gravitating macroscopic behavior of a conserved microscopic variable q. In this article, the gluon condensate of quantum c…
Lorentz violation and black-hole thermodynamics
G. Betschart, E. Kant, F. R. Klinkhamer
We consider nonstandard photons from nonbirefringent modified Maxwell theory and discuss their propagation in a fixed Schwarzschild spacetime background. This particular modificati…
New two-sided bound on the isotropic Lorentz-violating parameter of modified Maxwell theory
F. R. Klinkhamer, M. Schreck
There is a unique Lorentz-violating modification of the Maxwell theory of photons, which maintains gauge invariance, CPT, and renormalizability. Restricting the modified-Maxwell th…
f(R) Cosmology from q-Theory
F. R. Klinkhamer, G. E. Volovik
From a macroscopic theory of the quantum vacuum in terms of conserved relativistic charges (generically denoted by q^{(a)} with label a), we have obtained, in the low-energy limit,…
UHECR bounds on Lorentz violation in the photon sector
F. R. Klinkhamer
The aim of this brief review is to present a case study of how astrophysics data can be used to get bounds on Lorentz-violating parameters. For this purpose, a particularly simple…
Addendum: Ultrahigh-energy cosmic-ray bounds on nonbirefringent modified-Maxwell theory
F. R. Klinkhamer, M. Risse
Nonbirefringent modified-Maxwell theory, coupled to standard Dirac particles, involves nine dimensionless parameters, which can be bounded by the inferred absence of vacuum Cherenk…
Dynamic vacuum variable and equilibrium approach in cosmology
F. R. Klinkhamer, G. E. Volovik
A modified-gravity theory is considered with a four-form field strength F, a variable gravitational coupling parameter G(F), and a standard matter action. This theory provides a co…
Equilibrium boundary conditions, dynamic vacuum energy, and the Big Bang
F. R. Klinkhamer
The near-zero value of the cosmological constant Λin an equilibrium context may be due to the existence of a self-tuning relativistic vacuum variable q. Here, a cosmological nonequ…