A quantum-corrected black hole model arising from gravitational collapse in the framework of asymptotically safe gravity was recently proposed in Bonanno et al. (Phys Rev Lett 132:031401, 2024). Quantum corrected spacetime strongly deviates from the Schwarzschild solution near the event horizon, quickly merging with the Schwarzschild metric in the far region. While quasinormal modes and gray-body factors have been analyzed for test fields in this background, no such analysis has yet been performed for gravitational perturbations. In this work, we study axial gravitational perturbations of these black holes by modeling the effective quantum corrections through an anisotropic fluid energy-momentum tensor. We compute both quasinormal modes and gray-body factors, and show that quantum corrections enhance the quality factor of the oscillations, thereby making the quantum-corrected black hole a more efficient gravitational wave emitter. At asymptotically late times, the power-law decay is indistinguishable from Price’s tails, which behave as $$ \sim t^{-(2\ell + 3)} $$ , where $$ \ell $$ is the multipole number. We also demonstrate that quantum corrections lead to a suppression of the gray-body factors and examine the validity of the correspondence between gray-body factors and quasinormal modes.

Czechia

B. Lütfüoğlu

Quasinormal modes and gray-body factors for gravitational perturbations in asymptotically safe gravity

It has long been known that superpotential couplings in heterotic theories often vanish despite the absence of any known symmetry that would forbid them. We show that such structure is also exhibited by the matter field Kähler potential of these compactifications. We give an analytical analysis which provides some simple conditions under which certain terms, which would be expected to be present in the Kähler potential, vanish. Explicit examples of this phenomenon are provided, some of which are verifiable by other methods and some of which can only currently be accessed by these techniques. By studying the interplay of the structure we find with Higgsing transitions, we are able to show that this vanishing of Kähler potential terms can extend to all orders in a perturbative expansion in the matter fields.

United States

James Gray

Structure in the heterotic matter field Kähler potential

We study the radiative properties of a spherical and singularity-free black-hole geometry recently proposed in the literature. Contrary to the Schwarzschild spacetime, this geometry is geodesically complete and regular, and, instead of the singularity, it presents a minimal surface that connects a trapped (black-hole) with an antitrapped (white-hole) region. The geometry is characterized by two parameters: the Schwarzschild radius and another parameter that measures the area of the minimal surface. This parameter is related to certain corrections expected in the context of loop quantum gravity to the classical general-relativistic dynamics. We explicitly compute the spectrum of the Hawking radiation and the gray-body factor. Since the gravitational potential is shallower than in Schwarzschild, the emission spectrum turns out to be colder and purer (less gray). From this, we sketch the evaporation history of this geometry and conclude that, under certain assumptions, instead of completely evaporating, the black hole naturally leads to a remnant, which provides a possible resolution to the information-loss issue.

Spain

Asier Alonso-Bardaji

David Brizuela

Marc Schneider

Radiative properties of a nonsingular black hole: Hawking radiation and gray-body factor

We investigate the effect of potentially large distortions of the relic neutrino spectra on cosmological observables. To that end, we consider a phenomenological model of “gray” spectral distributions, described by a single parameter, which generalizes the traditional <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>y</mi></math>-distortions to possibly large negative values. Implementing these distortions in the primordial nucleosynthesis code primat, we can constrain the distortion parameter along with the presence of extra radiation, exploiting the complementarity of big bang nucleosynthesis and cosmic microwave background measurements to disentangle gravitational and nonthermal effects. These constraints rule out a distortion where more than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>1</mn><mo>/</mo><mn>2</mn></math> of the neutrinos’ energy density is replaced by dark radiation. Nonetheless, we find that large distortions, accompanied with extra radiation, are allowed—and even slightly preferred in some cases—by current cosmological observations. As this scenario would require substantial modifications to the physics of neutrino decoupling in the early Universe, these observational constraints call for a renewed attention on the possibility of large deviations from the standard cosmological model in the neutrino sector.

Gabriela Barenboim

Julien Froustey

France

Cyril Pitrou

Héctor Sanchis

Primordial neutrinos fade to gray: Constraints from cosmological observables

We calculate quasinormal modes and gray-body factors of a massive scalar field in the background of three compact objects in the Weyl gravity: Schwarzschild-like back holes, known as Mannheim–Kazanas solution, non-Schwrazschild-like black holes and traversable wormholes found recently in (Jizba and Mudruňka in Phys Rev D 110(12):124006, 2024, , [gr-qc]). We show that the spectrum of the massive field is qualitatively different from massless o ne both in the frequency and time domains. While the mass term leads to much longer lifetime of the modes, the arbitrarily long-lived modes, known as quasi-resonances, are not achieved.

Long-lived quasinormal modes and gray-body factors of black holes and wormholes in dark matter inspired Weyl gravity

Dark matter particles with a mass around 1 eV can decay into near-infrared photons. Utilizing available public blank sky observations from the NIRSpec IFU on the James Webb Space Telescope (JWST), we search for a narrow emission line due to decaying dark matter and derive leading constraints in the mass range 0.8–3 eV on the decay rate to photons, and more specifically, on the axion-photon coupling for the case of axionlike particles. We exclude <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi><mo>&lt;</mo><mn>3.5</mn><mo>×</mo><msup><mn>10</mn><mn>26</mn></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">s</mi></math> at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>DM</mi></mrow></msub><mo>≃</mo><mn>0.8</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi></mrow></math> and, in the case of axions, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>g</mi></mrow><mrow><mi>a</mi><mi>γ</mi><mi>γ</mi></mrow></msub><mo>&gt;</mo><mn>1.3</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>11</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>GeV</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>≃</mo><mn>2.2</mn><mtext> </mtext><mtext> </mtext><mi>eV</mi></mrow></math>. Our results do not rely on dedicated observations, rather we use blank sky observations intended for sky subtraction, and thus our reach may be automatically strengthened as JWST continues to observe.

Ryan Janish

Elena Pinetti

Hunting Dark Matter Lines in the Infrared Background with the James Webb Space Telescope

For compactifications of heterotic string theory, we elucidate simple cohomological conditions that lead to the vanishing of superpotential n-point couplings for all n. These results generalize some vanishing theorems for Yukawa couplings that have previously appeared in the literature to all higher orders. In some cases, these results are enough to show that certain fields do not appear in the perturbative superpotential at all. We illustrate our discussion with a number of concrete examples. In some cases, our results can be confirmed by showing that symmetries indeed forbid the couplings that vanish. In many, however, no such symmetries are known to exist and, as such, the infinite sets of vanishing couplings that are found are surprising from a four-dimensional perspective.

Vanishing conditions for higher order couplings in heterotic theories

In this work we investigate 5-dimensional theories obtained from M-theory on genus one fibered threefolds which exhibit twisted algebras in their fibers. We provide a base-independent algebraic description of the threefolds and compute light 5D BPS states charged under finite sub-algebras of the twisted algebras. We further construct the Jacobian fibrations that are associated to 6-dimensional F-theory lifts, where the twisted algebra is absent. These 6/5-dimensional theories are compared via twisted circle reductions of F-theory to M-theory. In the 5-dimensional theories we discuss several geometric transitions that connect twisted with untwisted fibrations. We present detailed discussions of <math> <msubsup> <mi>e</mi> <mn>6</mn> <mfenced> <mn>2</mn> </mfenced> </msubsup> </math> $$ {\mathfrak{e}}_6^{(2)} $$ , <math> <msubsup> <mi>so</mi> <mn>8</mn> <mfenced> <mn>3</mn> </mfenced> </msubsup> </math> $$ {\mathfrak{so}}_8^{(3)} $$ and <math> <msubsup> <mi>su</mi> <mn>3</mn> <mfenced> <mn>2</mn> </mfenced> </msubsup> </math> $$ {\mathfrak{su}}_3^{(2)} $$ twisted fibers and provide several explicit example threefolds via toric constructions. Finally, limits are considered in which gravity is decoupled, including Little String Theories for which we match 2-group symmetries across twisted T-dual theories.

Lara Anderson

Paul-Konstantin Oehlmann

Twisted Fibrations in M/F-theory

Geometric transitions between Calabi-Yau manifolds have proven to be a powerful tool in exploring the intricate and interconnected vacuum structure of string compactifications. However, their role in <math><mi>N</mi><mo>=</mo><mn>1</mn></math>, four-dimensional string compactifications remains relatively unexplored. In this work we present a novel proposal for transitioning the background geometry (including NS5-branes and holomorphic, slope-stable vector bundles) of four-dimensional, <math><mi>N</mi><mo>=</mo><mn>1</mn></math> heterotic string compactifications through a conifold transition connecting Calabi-Yau threefolds. Our proposal is geometric in nature but informed by the heterotic effective theory. Central to this study is a description of how the cotangent bundles of the deformation and resolution manifolds in the conifold can be connected by an apparent small instanton transition with a 5-brane wrapping the small resolution curves. We show that by a “pair creation” process 5-branes can be generated simultaneously in the gauge and gravitational sectors and used to describe a coupled minimal change in the manifold and gauge sector. This observation leads us to propose dualities for 5-branes and gauge bundles in heterotic conifolds which we then confirm at the level of spectrum in large classes of examples. While the 5-brane duality is novel, we observe that the bundle correspondence has appeared before in the target space duality exhibited by (0, 2) gauged linear sigma models. Thus our work provides a geometric explanation of (0, 2) target space duality.

Lara B. Anderson

Callum R. Brodie

Branes and bundles through conifold transitions and dualities in heterotic string theory

Non-simply connected Calabi-Yau threefolds play a central role in the study of string compactifications. Such manifolds are usually described by quotienting a simply connected Calabi-Yau variety by a freely acting discrete symmetry. For the Calabi-Yau threefolds described as complete intersections in products of projective spaces, a classification of such symmetries descending from linear actions on the ambient spaces of the varieties has been given in [16]. However, which symmetries can be described in this manner depends upon the description that is being used to represent the manifold. In [24] new, favorable, descriptions were given of this data set of Calabi-Yau threefolds. In this paper, we perform a classification of cyclic symmetries that descend from linear actions on the ambient spaces of these new favorable descriptions. We present a list of 129 symmetries/non-simply connected Calabi-Yau threefolds. Of these, at least 33, and potentially many more, are topologically new varieties.