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Stephen L. Adler

Publications and source records attributed to Stephen L. Adler.

At least 19 recordsLinked to original sources
arXiv2026

The mechanism for creating "dynamical gravastar" black hole mimickers also explains formation of "little red dots"

We argue that a high pressure phase transition of relativistic matter to a state with negative energy density, which leads to the formation of horizonless, globally unitary black hole mimickers, also gives rise to the appearance of ``little red dots''. The energy source for the dots is the release of latent energy from the phase transition, and their excess redness is a result of this release taking place in a central region of exponentially small positive $g_{00}$, and hence very high gravitational redshift.

gr-qc↗
arXiv2026

Asymptotic analysis of the "simulated horizon" segment of the Collins spiral

The Tolman-Oppenheimer-Volkoff (TOV) equations for a massless fluid take the form of a pair of coupled autonomous first order differential equations, which can be employed in a model for a ``dynamical gravastar'' black hole mimicker. The mimicker has no true horizon, but rather a ``simulated horizon'', outside which the geometry resembles a Schwarzschild black hole, but inside which the $g_{00}$ component of the metric is always positive and becomes exponentially small. Collins has reinterpreted the relevant TOV equations in terms of a two-dimensional flow with a spiral form, and Zöllner and Kämpfer have mapped the simulated horizon to a specific segment of the Collins spiral. We give here results of an asymptotic analysis, relating initial values at the small radius end of this spiral segment to the black hole mimicker mass and other parameters that emerge at the large radius kink in the TOV solution, which corresponds to the simulated horizon. A curious feature of this asymptotic mapping, given in Sec. IIB, is the appearance of power law behaviors with exponents of $1/5$ and $1/10$.

gr-qc↗
arXiv2025

Chen Ning Yang Retrospective

Chen-Ning Yang made important contributions to the theory of solvable models in statistical mechanics, including generalizations of the Bethe Ansatz, magnetization in the Ising model, the Lee-Yang circle theorem, and the Yang-Baxter equation. Most famously, Yang made transformative contributions to the current Standard Model of elementary particle interactions. The proposal of Yang and T. D. Lee, that left-right symetry (parity) is violated in weak particle decays, established that the primary currents involved in weak interactions are left handed. The work of Yang and R. L. Mills gave a framework for force carriers coupling to these currents that are non-Abelian generalizations of the electromagnetic photon, which unlike the electrically neutral photon, carry ``charges'' to which they self-couple . Two decades of work by others on quantization and mass-generation mechanisms then culminated in the Standard Model.

hep-ph↗
arXiv2024

Dynamical gravastar simulated horizon from the Tolman-Oppenheimer-Volkoff equation initial value problem with relativistic matter

We continue the study of "dynamical gravastars", constructed by solving the Tolman-Oppenheimer-Volkoff (TOV) equations with relativistic matter, undergoing a phase transition at high pressure to a state with negative energy density. We define the "simulated horizon" as the horizon-like structure that appears, and which is a well-defined concept within the class of static, spherically symmetric metrics. Since the "simulated horizon" occurs at a radius above where the pressure-induced phase transition is postulated to occur, it is solely a property of the TOV equation with relativistic matter, for appropriate small radius initial conditions. We survey the formation of a simulated horizon from this point of view. Rescaling the problem to fixed initial radius, we plot the "phase diagram" in the initial pressure--initial mass plane, showing the range of parameters where a simulated horizon dynamically forms. Reformulating the TOV equations in rescaling-invariant form yields improved numerical results for the "phase diagram", and gives a simplified model for further study consisting of a 2-dimensional autonomous system of first order differential equations. Our analysis gives a simple, natural answer to the question of how the radii where the phase transitions postulated in previous models of exotic compact objects are dynamically determined.

gr-qc↗
arXiv2024

Galaxy formation catalyzed by gravastars and the JWST, revisited

We have proposed that galaxy formation is catalyzed by the collision of infalling and outstreaming particles from leaky, horizonless astrophysical black holes, most likely gravastars, and based on this gave a model for the disk galaxy scale length. In this paper we modify our original scale length formula by including an activation probability $P$ for a collision to lead to nucleation of star formation. The revised formula extrapolates from early universe JWST data to late time data to within a factor of five, and suggests that galaxy dimensions should systematically get smaller as the observed redshift z increases. We also show that particles recycling through gravastars can lead to a reduction in the temperature of the surrounding gas, through a ``heat pump'' refrigeration effect. This can trigger galaxy formation through enhanced star formation in the vicinity of the gravastar.

gr-qc↗
arXiv2024

Equation of state, and atomic electron effective potential, for a Weyl scaling invariant dark energy

A key attribute of dark energy is the equation of state parameter $w={\rm pressure}/{\rm energy~density}$, and this has been recently measured observationally, giving values close to $-1$. In this paper we calculate the $w$ parameter characterizing the novel Weyl scaling invariant dark energy that we have analyzed in a series of papers, and show that it is compatible with experiment. We also derive the atomic electron effective potential induced by dark energy from the electron geodesic equation, which can be applied to the evaluation of energy level shifts in Rydberg atoms.

gr-qc↗
arXiv2024

Hidden Sector Dark Matter Realized as a Twin of the Visible Universe With Zero Higgs Vacuum Expectation

We propose that the universe contains two identical sets of particles and gauge interactions, coupling only through gravitation, which differ by their Higgs potentials. We postulate that because of underlying symmetries, the two sectors when uncoupled have Higgs potentials that lie at the boundary between phases with nonzero and zero Higgs vacuum expectation. Turning on the coupling between the two sectors can break the degeneracy, pushing the Higgs potential in one sector into the domain of nonzero Higgs expectation (giving the visible sector), and pushing the Higgs potential in the other sector into the domain of zero Higgs expectation (giving the dark sector). The least massive baryon in the dark sector will then be a candidate self-interacting dark matter particle.

hep-ph↗
arXiv2023

Dynamical gravastars may evade no-go results for exotic compact objects, together with further analytical and numerical results for the dynamical gravastar model

Using graphs plotted from the Mathematica notebooks posted with our paper ``Dynamical Gravastars'', we show that a dynamical gravastar has no hard surface, and that a second light sphere resides in the deep interior where there is maximum time dilation. These facts may permit dynamical gravastars to evade no-go results for exotic compact objects relating to light leakage inside the shadow, and nonlinear instabilities arising from an interior light sphere. Testing these surmises will require further detailed modeling calculations, beyond what we commence in this paper, using the numerical dynamical gravastar solution. We also discuss the effect of replacing the sigmoidal function in the gravastar calculation by a unit step function, and we analyze why the dynamical gravastar evades the singularities predicted by the Penrose and Hawking singularity theorems, despite satisfying both the null and strong energy conditions. We then give a simplified two-step process for tuning the initial value $ν(0)={\rm nuinit}$ to achieve $ν(\infty)=0$, and give exact integrals for the pressure differential equation in terms of $ν(r)$ in the interior and exterior regions. Finally, we briefly discuss an extension of the model that includes an external shell of massive particles.

gr-qc↗
arXiv2023

Dynamical Gravastars

We combine the ideas of a Weyl scaling invariant dark energy action, which eliminates black hole horizons, with the ``gravastar'' idea of a jump in the hole interior from a normal matter equation of state to an equation of state where pressure plus density approximately sum to zero. Using the Tolman-Oppenheimer-Volkoff equation, which requires continuous pressure, we present Mathematica notebooks in which the structure of the gravastar is entirely governed by the action and the equation of state, with the radii where structural changes occur emerging from the dynamics, rather than being specified in advance. The notebooks work even with zero cosmological constant, but when the cosmological constant is nonzero, there is a very small black hole ``wind'' that we calculate by a relativistic extension of standard pressure driven isothermal stellar wind theory.

gr-qc↗
arXiv2022

Solar system relativity tests, formulas for light deflection by a central mass, and modification of the lens equation, for a Weyl scaling invariant dark energy

We estimate the changes in solar system tests of general relativity when "dark energy" arises from a Weyl scaling invariant action, using the modified Schwarzschild-like spherically symmetric solution obtained in this case by Adler and Ramazano\vglu. We show that the standard results of general relativity are modified by amounts that are far below current experimental errors. However, because the metric is not conformally flat when the central mass $M$ vanishes, there is a contribution to light deflection proportional to the cosmological constant $Λ$, with opposite sign to the one proportional to $M$. This could have implications for gravitational lensing in cosmological contexts, so we have calculated the corresponding correction to the "lens equation" for gravitational lensing. We also give formulas for the light deflection angle through order $ΛM$, assuming a parameterized spherically symmetric metric for the external region of the central mass.

gr-qc↗
arXiv2022

Cosmological constant corrections to the photon sphere and black hole shadow radii

We review the equations determining the photon sphere radius and the black hole shadow radius, and calculate the cosmological constant corrections arising when the dark energy action has the usual form, and when dark energy arises from a Weyl scaling invariant dark energy action. For black hole targets of the Event Horizon Telescope, the corrections are very small.

gr-qc↗
arXiv2022

Are Astrophysical "Black" Holes Leaky?

We continue a study by Adler and Ramazano\uglu (AR) of "black" holes as modified by a scale invariant dark energy action. For the spherically symmetric Schwarzschild-like case, (AR) found that there is no event horizon; hence spacetime is not divided by the "black" hole into causally disconnected regions. We review the formalism for locating trapped surfaces and apparent horizons, and show that the modified "black" hole has no trapped surfaces. Thus one suspects that it is "leaky", and that there will be a "black hole wind" of particles streaming out from the location of the nominal horizon. This will have astrophysical consequences, for example, the wind may feed and stabilize star formation in the vicinity of the "black" hole. We initiate a study of the stationary axially-symmetric rotating "black" hole as modified by a scale invariant dark energy action, i.e, one that is Kerr-like. To set up the axial case, we note that the conserving completion of the dark energy stress energy tensor can be calculated algebraically by solving a $2 \times 2$ matrix equation. Using Mathematica we calculate and simplify the modified system of Einstein equations for the axial case in quasi-isotropic coordinates, and give appropriate boundary conditions. Solution of these equations, which may require developing a special purpose numerical program, is rendered tricky by a residual general coordinate invariance of quasi-isotropic coordinates. This leads to the interesting mathematical question of representing a positive planar function as the gradient squared of a harmonic function.

gr-qc↗
arXiv2022

A mechanism for a "leaky" black hole to catalyze galaxy formation

In the gravitational field of a Schwarzschild-like black hole, particles infalling from rest at infinity, and black hole "wind" particles with relativistic velocity leaking radially out from the nominal horizon, both have the same magnitude of velocity at any radius from the hole. Hence when equally massive infalling and wind particles collide at any radius, they yield collision products with zero center of mass radial velocity, which can then nucleate star formation at the collision radius. We suggest that this gives a mechanism by which a central black hole can catalyze galaxy formation. For disk galaxies, this mechanism explains the observed approximately exponential falloff of the surface brightness with radius, and gives an estimate of the associated scale length.

gr-qc↗
arXiv2022

A One-Dimensional Model for Star Formation Near a "Leaky" Black Hole

In the presence of a Weyl scaling invariant cosmological action, black holes no longer have an event horizon and an apparent horizon. So they have no trapped surfaces, and may be "leaky", emitting a "black hole wind" which could lead to star formation in the neighborhood of the hole. In this paper we formulate and analyze a one-dimensional model for star formation resulting from a postulated outgoing black hole particle flux, incident on a distant spherical surface modeled as a set of planar disks surrounding the hole. Using the Toomre analysis of the Jeans instability of a disk, we compute conditions for a disk collapse instability and estimate the collapse time. We suggest a mechanism for giving the disk angular momentum around the central black hole. This gives a possible explanation for the puzzling observation of young stars forming in the vicinity of the black hole Sagittarius A* central to the Milky Way galaxy.

gr-qc↗
arXiv2021

Is "Dark Energy" a Quantum Vacuum Energy?

We review the origins, motivations, and implications for cosmology and black holes, of our proposal that "dark energy" is not a quantum vacuum energy, but rather arises from a Weyl scaling invariant nonderivative component of the gravitational action.

gr-qc↗
arXiv2021

Covariance Group for Null Geodesic Expansion Calculations, and its Application to the Apparent Horizon

We show that the recipe for computing the expansions $θ_\ell$ and $θ_n$ of outgoing and ingoing null geodesics normal to a surface admits a covariance group with nonconstant scalar $κ(x)$, corresponding to the mapping $θ_\ell \to κθ_\ell$, $θ_n \to κ^{-1} θ_n$. Under this mapping, the product $θ_\ell θ_n$ is invariant, and thus the marginal surface computed from the vanishing of $θ_\ell$, which is used to define the apparent horizon, is invariant. This covariance group naturally appears in comparing the expansions computed with different choices of coordinate system.

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