A no-go theorem shows that negative effective mass squared for the vector field in vector-tensor gravity always accompanies ghost or gradient instabilities, blocking spontaneous vectorization in stationary axisymmetric black holes.
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Evasion of No-Hair Theorems and Novel Black-Hole Solutions in Gauss-Bonnet Theories
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abstract
We consider a general Einstein-scalar-GB theory with a coupling function f(\phi). We demonstrate that black-hole solutions appear as a generic feature of this theory since a regular horizon and an asymptotically-flat solution may be easily constructed under mild assumptions for f(\phi). We show that the existing no-hair theorems are easily evaded, and a large number of regular, black-hole solutions with scalar hair are then presented for a plethora of coupling functions f(\phi).
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Gravitational memory from hairy binary black hole mergers in scalar-Gauss-Bonnet gravity differs from GR by a few percent due to altered nonlinear dynamics, with direct scalar contributions suppressed, and including memory increases GR-sGB mismatch by more than an order of magnitude.
In Einstein-scalar-Maxwell theories, charged compact binaries produce gravitational waveforms containing a leading -1 post-Newtonian dipole correction controlled by one deviation parameter b.
Exact non-singular black holes from the phantom DBI field evaporate to gram-mass relics, opening a new mass window for primordial black holes as dark matter.
A covariant framework reveals non-closed scalar charges with bulk contributions in ESGB black holes that become closed under shift symmetry and interpret spontaneous scalarization via the Smarr formula.
Kerr black holes in an EsGB model without linear instability undergo nonlinear scalarization above spin 0.5, existing in a finite low-mass high-spin wedge rather than a narrow band.
Charge-dependent scalarization of EEH black holes yields stable scalarized branches for 0<q<1.115 with positive α and for q>1.115 with negative α.
Linear coupling and rotation in scalar-tensor theories produce a complex phase transition landscape for scalarized neutron stars, with rotation increasing critical masses and Landau theory revealing overlooked solution branches.
Kerr-Newman black holes in EMS theory with scalar potential scalarize for spins below a threshold set by charge, scalar mass, and coupling strength.
Combining regular black hole metrics with memory burden suppresses evaporation and opens a 10^6-10^8 g PBH mass window that can comprise all dark matter.
Nonlinearly scalarized black holes exist in EsGB theory for couplings ζ(φ)=αφ⁴−βφ⁸ and ζ(φ)=αφ⁴−βφ⁶ (but not pure quartic), with instability thresholds for Gaussian pulses and universal probe-limit branches that depend on β when backreaction is included.
In scalar Gauss-Bonnet gravity, black hole solutions below a tunable minimum mass lose hyperbolicity in perturbations, corresponding to EFT breakdown, but scalar charge stays bounded above.
Two extremal black holes with secondary scalar hair are identified in a two-U(1) Einstein-Maxwell-scalar theory using scalarization and entropy function methods, implying primary hair is difficult to obtain.
Charged qOS black holes undergo Gauss-Bonnet scalarization in two regimes, producing linearly stable scalarized solutions for specific ranges of the action parameter α and coupling λ.
Nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory undergo a first-order phase transition from Schwarzschild black holes with non-zero latent heat.
citing papers explorer
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No-go theorem for spontaneous vectorization
A no-go theorem shows that negative effective mass squared for the vector field in vector-tensor gravity always accompanies ghost or gradient instabilities, blocking spontaneous vectorization in stationary axisymmetric black holes.
-
Gravitational Memory from Hairy Binary Black Hole Mergers
Gravitational memory from hairy binary black hole mergers in scalar-Gauss-Bonnet gravity differs from GR by a few percent due to altered nonlinear dynamics, with direct scalar contributions suppressed, and including memory increases GR-sGB mismatch by more than an order of magnitude.
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Inspiral gravitational waveforms from charged compact binaries with scalar hair
In Einstein-scalar-Maxwell theories, charged compact binaries produce gravitational waveforms containing a leading -1 post-Newtonian dipole correction controlled by one deviation parameter b.
-
Exact, non-singular black holes from a phantom DBI Field as primordial dark matter
Exact non-singular black holes from the phantom DBI field evaporate to gram-mass relics, opening a new mass window for primordial black holes as dark matter.
-
Spin-Induced Nonlinear Scalarization of Kerr Black Holes in Einstein-scalar-Gauss-Bonnet Gravity
Kerr black holes in an EsGB model without linear instability undergo nonlinear scalarization above spin 0.5, existing in a finite low-mass high-spin wedge rather than a narrow band.
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Charge-dependent scalarization of Einstein- Euler-Heisenberg black holes
Charge-dependent scalarization of EEH black holes yields stable scalarized branches for 0<q<1.115 with positive α and for q>1.115 with negative α.
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Phase transition structure of scalarized neutron stars: the effect of rotation and linear coupling
Linear coupling and rotation in scalar-tensor theories produce a complex phase transition landscape for scalarized neutron stars, with rotation increasing critical masses and Landau theory revealing overlooked solution branches.
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Spin-charge induced scalarization of Kerr-Newman black holes in the Einstein-Maxwell-scalar theory with scalar potential
Kerr-Newman black holes in EMS theory with scalar potential scalarize for spins below a threshold set by charge, scalar mass, and coupling strength.
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Existence of nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory with polynomial couplings
Nonlinearly scalarized black holes exist in EsGB theory for couplings ζ(φ)=αφ⁴−βφ⁸ and ζ(φ)=αφ⁴−βφ⁶ (but not pure quartic), with instability thresholds for Gaussian pulses and universal probe-limit branches that depend on β when backreaction is included.
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Minimum mass, maximum charge and hyperbolicity in scalar Gauss-Bonnet gravity
In scalar Gauss-Bonnet gravity, black hole solutions below a tunable minimum mass lose hyperbolicity in perturbations, corresponding to EFT breakdown, but scalar charge stays bounded above.
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Scalarized extremal black holes in the Einstein-Maxwell-scalar theory with two U(1) fields
Two extremal black holes with secondary scalar hair are identified in a two-U(1) Einstein-Maxwell-scalar theory using scalarization and entropy function methods, implying primary hair is difficult to obtain.
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Gauss-Bonnet scalarization of charged qOS-black holes
Charged qOS black holes undergo Gauss-Bonnet scalarization in two regimes, producing linearly stable scalarized solutions for specific ranges of the action parameter α and coupling λ.
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Thermodynamics and phase transitions of nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory
Nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory undergo a first-order phase transition from Schwarzschild black holes with non-zero latent heat.
- On cosmological properties of black-hole hair in linearly coupled scalar-Gauss-Bonnet theory
- Regular hairy black holes by gravitational decoupling: Bardeen and Minkowski-core seeds