arXiv subjects

Marek Wazny

Publications and source records attributed to Marek Wazny.

4 recordsLinked to original sources

arXiv2026

Black holes with regular scalar hair in Brans-Dicke gravity via the Herglotz variational principle

Brans-Dicke theory is reformulated within the Herglotz variational principle (HVP), and an exact black hole solution with scalar hair is obtained for $ω_{0}=0$ and vanishing potential $V(ϕ)=0$. The scalar profile is strictly positive and the resulting stealth Schwarzschild solution arises without fixing the otherwise arbitrary Herglotz function $η(r)$. Motivated by the weak-field limit, the explicit choice $η(r)=η_{0}(r-2M)^k/r^{k+2}$, with $η_0$ a constant of dimension length, produces a scalar field configuration remaining regular at the black hole horizon. Consequently, the HVP provides a new mechanism for evading standard no-hair theorems in scalar-tensor theories.

gr-qc↗

arXiv2026

Herglotz-type $f(R,T)$ gravity

The non-conservation of the energy-momentum tensor in $f(R,T)$ gravity can be interpreted as an effective manifestation of dissipation. Motivated by this, we propose a new formulation of $f(R,T)$ gravity based on the Herglotz variational principle, which extends the usual {Hamilton} variational principle to dissipative systems by allowing the Lagrangian to depend explicitly on the action. The resulting gravitational field equations extend those of $f(R,T)$ gravity by including Herglotz contributions. In the Newtonian limit, these contributions modify the gravitational potential, allowing us to constrain the Herglotz vector through Mercury's perihelion precession and the relativistic light deflection. The Herglotz corrections lead to a scaling law consistent with observations from the Cassini spacecraft. Examining two representative cosmological models, the Herglotz vector effectively reduces to a single function that, under suitable conditions, can play the role of a cosmological constant, providing an alternative mechanism for the Universe's accelerated expansion. Within the Herglotz variational approach, the linear $f(R,T)=R+αT$ model, previously ruled out in the standard formulation due to its fixed deceleration parameter, becomes consistent with observations {for a certain choice of the Herglotz vector.

gr-qc↗

arXiv2026

Conservative cosmology in scalar-tensor Herglotz $f(R,T)$ gravity

The scalar-tensor representation of $f(R,T)$ gravity is extended to incorporate the Herglotz variational principle. The field equations are derived in both the geometric and scalar-tensor frameworks. Although the divergence of the energy-momentum tensor in matter-geometry coupling theories is generally nonvanishing, conservation can be achieved through the introduction of the Herglotz vector. The generalized Friedmann equations in scalar-tensor Herglotz $f(R,T)$ theory are obtained, and a conservative cosmological model is shown to be consistent with late-time observational data. Comparisons with analogous nonconservative models and with the standard $Λ$CDM model are also provided.

gr-qc↗

arXiv2025

Hot Jupiters are asynchronous rotators

Hot Jupiters are typically assumed to be synchronously rotating, from tidal locking. Their thermally-driven atmospheric winds experience Lorentz drag on the planetary magnetic field anchored at depth. We find that the magnetic torque does not integrate to zero over the entire atmosphere. The resulting angular momentum feedback on the bulk interior can thus drive the planet away from synchronous rotation. Using a toy tidal-ohmic model and atmospheric GCM outputs for HD189733b, HD209458b and Kepler7b, we establish that off-synchronous rotation can be substantial at tidal-ohmic equilibrium for sufficiently hot and/or magnetized hot Jupiters. Potential consequences of asynchronous rotation for hot Jupiter phenomenology motivate follow-up work on the tidal-ohmic scenario with approaches that go beyond our toy model.

astro-ph.EP↗