We study the effect of Spontaneous Lorentz Symmetry Breaking (SLSB) on Primordial Gravitational Waves (PGWs) generated during inflation. The SLSB is induced by a time-like Bumblebee vector field which is non-minimally coupled to the Ricci tensor in the Friedmann-Lemaître-Robertson-Walker background. The power spectrum and GW amplitude are computed to investigate how Lorentz violation leaves observable imprints. We calculate the GW strain amplitude over frequencies <math altimg='si1.svg'><mo stretchy='false'>(</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>10</mn></mrow></msup><mspace width='0.25em' /><mrow><mi mathvariant='normal'>Hz</mi></mrow><mo>,</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>4</mn></mrow></msup><mspace width='0.25em' /><mrow><mi mathvariant='normal'>Hz</mi></mrow><mo stretchy='false'>)</mo></math>, for a range of the dimensionless Lorentz-violating parameter, <math altimg='si2.svg'><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>3</mn></mrow></msup><mo>&#8804;</mo><mi>l</mi><mo>&#8804;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>4</mn></mrow></msup></math>, which essentially comes from a slight sensitivity to the equation of state for dark energy. For positive <italic>l</italic> values, the amplitude of GW shows a mild suppression compared to the standard cosmological scenario ( <math altimg='si3.svg'><mi>l</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math>). This effect could be observable with detectors like SKA, <italic>&#956;</italic>-Ares, and BBO. Conversely, negative <italic>l</italic> values amplify the GW amplitude, enhancing detectability by both SKA, <italic>&#956;</italic>-Ares, and BBO, as well as by THEIA and DECIGO. Notably, the GW strain amplitude increases by an order of magnitude as <italic>l</italic> moves from 0 to <math altimg='si4.svg'><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>3</mn></mrow></msup></math>, improving prospects for detection in high-sensitivity detectors like THEIA and DECIGO.

Iran

Mohsen Khodadi

Italy

Gaetano Lambiase

Leonardo Mastrototaro

Tanmay Kumar Poddar

Primordial gravitational waves from spontaneous Lorentz symmetry breaking

<p>Core-collapse supernovae (SNe) provide a unique environment to study feebly interacting particles (FIPs) such as axionlike particles (ALPs), sterile neutrinos, and dark photons (DPs). This paper focuses on heavy FIPs produced in SNe, whose decay produces electrons and positrons, generating observable secondary signals during their propagation and annihilation. We focus on the in-flight annihilation of positrons, which emerge as the most significant contribution to the resulting <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray spectrum. Using data from COMPTEL and EGRET, we derive the most stringent bounds on the FIP-electron couplings for heavy ALPs, sterile neutrinos, and DPs. These results strengthen existing bounds by one to two orders of magnitude, depending on the FIP model.</p>

United Kingdom

Shyam Balaji

Sweden

Pierluca Carenza

Spain

Pedro De la Torre Luque

Alessandro Lella

In-flight positron annihilation as a probe of feebly interacting particles

<p>The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray emission originating from in-flight annihilation (IA) of positrons is a powerful observable for constraining high-energy positron production from exotic sources. By comparing diffuse <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray observations of INTEGRAL, COMPTEL, and EGRET to theoretical predictions, we set the most stringent constraints on electrophilic feebly interacting particles, thereby proving IA as a valuable probe of new physics. In particular, we extensively discuss the case of MeV-scale sterile neutrinos, where IA sets the most stringent constraints, excluding <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>μ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>≳</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>13</mn></mrow></msup></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>τ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>≳</mo><mn>2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>13</mn></mrow></msup></mrow></math> for sterile neutrinos mixed with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> neutrinos, respectively. These constraints improve existing limits by more than an order of magnitude. We briefly discuss the application of these results to a host of exotic positron sources such as dark photons, axionlike particles, primordial black holes, and sub-GeV dark matter.</p>

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math> rays from in-flight positron annihilation as a probe of new physics

Sterile neutrinos with masses up to <math><mi>O</mi><mo>(</mo><mn>100</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> can be copiously produced in a supernova (SN) core through the mixing with active neutrinos. In this regard, the SN 1987A detection of neutrino events has been used to put constraints on active-sterile neutrino mixing, exploiting the well-known SN cooling argument. We refine the calculation of this limit including neutral current interactions with nucleons, which constitute the dominant channel for sterile neutrino production. We also include, for the first time, the charged current interactions between sterile neutrinos and muons, relevant for the production of sterile neutrinos mixed with muon neutrinos in the SN core. Using the recent modified luminosity criterion, we extend the bounds to the case where sterile states are trapped in the stellar core. Additionally, we study the decays of heavy sterile neutrinos, affecting the SN explosion energy and possibly producing a gamma-ray signal. We also illustrate the complementarity of our new bounds with cosmological bounds and laboratory searches.

Germany

Giuseppe Lucente

Alessandro Mirizzi

France

Pasquale Dario Serpico

Comprehensive constraints on heavy sterile neutrinos from core-collapse supernovae

The study of neutrino pair annihilation into electron-positron pairs ( $$\nu {\bar{\nu }}\rightarrow e^-e^+$$  <math> <mrow> <mi>ν</mi> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mo>→</mo> <msup> <mi>e</mi> <mo>-</mo> </msup> <msup> <mi>e</mi> <mo>+</mo> </msup> </mrow> </math>  ) is astrophysically well-motivated because it is a possible powering mechanism for the gamma-ray bursts (GRBs). In this paper, we estimate the gamma-ray energy deposition rate (EDR) arising from the annihilation of the neutrino pairs in the equatorial plane of a slowly rotating black hole geometry modified by the broken Lorentz symmetry (induced by a background bumblebee vector field). More specifically, owing to the presence of a dimensionless Lorentz symmetry breaking (LSB) parameter l arising from nonminimal coupling between the bumblebee field with nonzero vacuum expectation value and gravity, the metric solution in question differs from the standard slowly rotating Kerr black hole. By idealizing the thin accretion disk temperature profile in the two forms of isothermal and gradient around the bumblebee gravity-based slow rotating black hole, we investigate the influence of spontaneous LSB on the  $$\nu {\bar{\nu }}$$  <math> <mrow> <mi>ν</mi> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>  -annihilation efficiency. For both profiles, we find that positive values of LSB parameter  $$l&gt;0$$  <math> <mrow> <mi>l</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math>   induce an enhancement of the EDR associated with the neutrino-antineutrino annihilation. Therefore, the process of powering the GRBs jets around bumblebee gravity modified slowly rotating geometry is more efficient in comparison with standard metric. Using the observed gamma-ray luminosity associated with different GRBs types (short, long, and ultra-long), we find, through the analysis of the EDR in the parameter space  $$l-a$$  <math> <mrow> <mi>l</mi> <mo>-</mo> <mi>a</mi> </mrow> </math>   ( $$a^2\ll 1$$  <math> <mrow> <msup> <mi>a</mi> <mn>2</mn> </msup> <mo>≪</mo> <mn>1</mn> </mrow> </math>  ), some allowed ranges for the LSB parameter l.

Spontaneous Lorentz symmetry breaking effects on GRBs jets arising from neutrino pair annihilation process near a black hole

Motivated by recent work on the Modified Maxwell (ModMax) black holes [Phys Lett B 10.1016/j.physletb.2020.136011], which are invariant in duality rotations and conformal transformations founded in [Phys Rev D 10.1103/PhysRevD.102.121703], we probe its effects on the shadow cast, weak field gravitational lensing, and neutrino propagation in its vicinity. Using the EHT data for the shadow diameter of Sgr. A* and M87*, and LIGO/VIRGO experiments for the dyonic ModMax black hole perturbations, we find constraints for ModMax parameters such as  $$Q_\text {m}$$  <math> <msub> <mi>Q</mi> <mtext>m</mtext> </msub> </math>   and the screening factor  $$\gamma $$  <math> <mi>γ</mi> </math>  . We also analyze how the shadow radius behaves as perceived by a static observer and one that is comoving with the cosmic expansion. The effect of the ModMax parameters is constant for a static observer, and we found That it varies when the observer is comoving with cosmic expansion. We also analyzed its effect on the weak deflection angle by exploiting the Gauss–Bonnet theorem and its application to Einstein ring formation. We also consider the finite distance effect and massive particle deflection. Our results indicate that the far approximation of massive particle gives the largest deflection angle and amplifies the effect of  $$Q_\text {m}$$  <math> <msub> <mi>Q</mi> <mtext>m</mtext> </msub> </math>   and  $$\gamma $$  <math> <mi>γ</mi> </math>  . Then we also calculate the quasinormal modes and greybody bounds which encode unique characteristic features of the dyonic ModMax black hole. With the advent of improving space technology, we reported that it is possible to detect the deviation caused through the shadow cast, Einstein rings, quasinormal modes, and neutrino oscillations.

Philippines

Reggie Pantig

Türkiye

Ali Övgün

Shadow, lensing, quasinormal modes, greybody bounds and neutrino propagation by dyonic ModMax black holes

The detection of very high-energy neutrinos by IceCube experiment supports the existence of a comparable gamma-ray counterpart from the same cosmic accelerators. Under the likely assumption that the sources of these particles are of extragalactic origin, the emitted photon flux would be significantly absorbed during its propagation over cosmic distances. However, in the presence of photon mixing with ultra-light axion-like-particles (ALPs), this expectation would be strongly modified. Notably, photon-ALP conversions in the host galaxy would produce an ALP flux which propagates unimpeded in the extragalactic space. Then, the back-conversion of ALPs in the Galactic magnetic field leads to a diffuse high-energy photon flux. In this context, the recent detection of the diffuse high-energy photon flux by the Large High Altitude Air Shower Observatory (LHAASO) allows us to exclude at the  $$95\%$$  <math> <mrow> <mn>95</mn> <mo>%</mo> </mrow> </math>   CL an ALP-photon coupling  $$g_{a\gamma } &gt; rsim 3.9$$  <math> <mrow> <msub> <mi>g</mi> <mrow> <mi>a</mi> <mi>γ</mi> </mrow> </msub> <mo>≳</mo> <mn>3.9</mn> </mrow> </math>  – $$7.8 \times 10^{-11}~\mathrm {GeV^{-1}}$$  <math> <mrow> <mn>7.8</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>11</mn> </mrow> </msup> <mspace width="3.33333pt"></mspace> <msup> <mi>GeV</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </mrow> </math>   for  $$m_{a}\lesssim 4\times 10^{-7}~\textrm{eV}$$  <math> <mrow> <msub> <mi>m</mi> <mi>a</mi> </msub> <mo>≲</mo> <mn>4</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>7</mn> </mrow> </msup> <mspace width="3.33333pt"></mspace> <mtext>eV</mtext> </mrow> </math>  , depending on the assumptions on the magnetic fields and on the original gamma-ray spectrum. This new bound is complementary with other ALP constraints from very-high-energy gamma-ray experiments and sensitivities of future experiments.

Marco Chianese

Denmark

Damiano Fiorillo

Gennaro Miele

Daniele Montanino

Constraining axion-like particles with the diffuse gamma-ray flux measured by the Large High Altitude Air Shower Observatory

Black holes can accumulate a large amount of energy, responsible for highly energetic astrophysical phenomena. Although the Blandford–Znajek is considered to date the leading mechanism for powering jets and GRBs, recently fast magnetic reconnection (MR) of the magnetic field was proposed as a new way to extract energy. In this paper, we investigate this phenomena in a bumblebee Kerr–Sen BH, which differentiates from standard Kerr solution via a Lorentz symmetry breaking parameter  $$\ell $$  <math> <mi>ℓ</mi> </math>   and an electric charge one b. We find that the presence of the charge parameter strongly changes the simple Kerr case, making this extraction mechanism possible even for not extremely rotating black holes ( $$a\sim 0.7$$  <math> <mrow> <mi>a</mi> <mo>∼</mo> <mn>0.7</mn> </mrow> </math>  ). We also show that, under appropriate circumstances, MR is more efficient compared to the Blandford–Znajek mechanism. We finally compare these results with dark energy (quintessence) black-hole solutions. In this case, we find that a Kerr black hole is indistinguishable from a rotational Kiselev one, whatever the energy-matter that surrounds it (including ordinary matter, such as dust and radiation).

Amodio Carleo

Energy extraction via magnetic reconnection in Lorentz breaking Kerr–Sen and Kiselev black holes

We consider axions coupled to nucleons and photons only through the nucleon electric-dipole moment (EDM) portal. This coupling is a model-independent feature of QCD axions, which solve the strong <math><mi>C</mi><mi>P</mi></math> problem, and might arise as well in more general axionlike particle setups. We revise the supernova (SN) axion emission induced by the nucleon EDM coupling and refine accordingly the SN 1987A bound. Furthermore, we calculate the axion flux from a future Galactic SN and show that it might produce a peculiar and potentially detectable gamma-ray signal in a large underground neutrino detector such as the proposed Hyper-Kamiokande. The possibility to detect such a signal offers a way to search for an oscillating nucleon EDM complementary to CASPERe, without relying on the assumption that axions are a sizeable component of the dark matter. Furthermore, if axions from SN produce an observable signal, they could also lead to an amount of cosmological extra radiation observable in future cosmic surveys.

Luca Di Luzio

United States

Maurizio Giannotti

Axion signatures from supernova explosions through the nucleon electric-dipole portal

Feebly interacting particles with masses with <math><mrow><mi>O</mi><mo>(</mo><mn>10</mn><mi>–</mi><mn>100</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math> can be copiously produced by core-collapse supernovae (SNe). In this paper we consider the case of MeV-ish sterile neutrinos and dark photons mixed with ordinary neutrinos and photons, respectively. Furthermore, both sterile neutrinos and dark photons may decay into positrons on their route to Earth. Such positrons would annihilate with electrons in the Galactic medium and contribute to the photon flux in the 511 keV line. Using the spectrometer on INTEGRAL observation of this line improves the bounds on the mixing parameters for these particles by several orders of magnitude below what is already excluded by the SN 1987A energy-loss argument.

Francesca Calore

Joerg Jaeckel

511 keV line constraints on feebly interacting particles from supernovae