We show that flying-focus fields can be obtained from complex conformal transformation of plane waves, and that solutions of the massless wave equation in the so-obtained fields are, correspondingly, conformal transformations of the Volkov solutions. This leads to the result that photon emission amplitudes in a totally depleting flying-focus beam may be computed directly from the corresponding plane-wave amplitudes by taking a simple Gaussian average over certain momentum variables. In effect, this gives a way of introducing focusing effects into strong-field QED calculations “for free.” The extension of these results to scattering amplitudes including only partial depletion is discussed and some first results presented in the anti-self-dual limit.

United Kingdom

Tim Adamo

Anton Ilderton

Adam Noble

Scattering and depletion in a flying focus from conformal transformations

Beyond the standard model particles can imprint a temporary early matter-dominated epoch on a stochastic gravitational-wave background. For a freely propagating background whose production has ceased, we show that the resulting feature contains two characteristic frequencies that determine the particle decay rate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Γ</mi></math> and the abundance-weighted mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Y</mi><mi>i</mi></msub><mi>M</mi></math>, independently of the microphysical origin of the gravitational-wave source. Using numerical scans, we derive semianalytic relations between these characteristic frequencies and the beyond the standard model particle parameters, and quantify the parameter ranges over which these relations remain valid. For backgrounds that remain actively sourced, the end of early matter domination continues to define a source-independent cosmological frequency scale controlled by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Γ</mi></math>, although the second feature, and hence the inference of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Y</mi><mi>i</mi></msub><mi>M</mi></math>, is source dependent. Once a particle model and production mechanism are specified, the measured combinations can be translated into masses and microscopic couplings. Remarkably, decay lengths targeted by upcoming long-lived-particle searches map directly onto the nanohertz range in which NANOGrav has reported evidence for a stochastic gravitational-wave background.

Anish Ghoshal

Angus Spalding

Graham White

Irreducible gravitational wave background as a particle detector

The Improved Quantum Null Energy Condition (INEC) was recently derived from the (restricted) quantum focusing conjecture (QFC), and is a statement about the energy-momentum tensor (EMT) of field theories in Minkowski space-time. It extends the quantum null energy condition (QNEC), and includes the possibility of expanding or contracting geodesics. Treating the INEC as a field theory inequality, we use the properties of relative entropy and modular Hamiltonian associated with null deformation of the sphere to recast it as an integrated inequality. At leading order in a perturbation of the vacuum, this inequality becomes a weighted positivity condition on the smeared null energy. As the underlying single-segment light-cone operator is unbounded below for $\textit{d}$ > 2, we pass to the Lorentzian cylinder $\textit{ℝ}$ × $\textit{S}$ , where the operator is well-defined. We verify that the INEC holds explicitly in the thermal state, in both the perturbative and high-temperature regimes. Furthermore, using the QNEC and INEC as a basis, we briefly speculate about a possible modified Quantum Focusing Conjecture.

Israel

Ido Ben-Dayan

Ayushi Srivastava

Towards a proof of the improved quantum null energy condition

In this paper, we introduce a commensurable and non-degenerate double sine-Gordon model, in which a partial breaking of vacuum degeneracy provides a mechanism for the emergence of static multi-kinks. These multi-kinks $\textit{K}$ are stable field configurations with internal structure, consisting of $\textit{n}$ localized energy packets with well-defined separations. The properties of the multi-kinks are thoroughly analyzed, including the novel phenomenology that arises during their collisions. In particular, we observe the emergence of long-lived composite oscillons that reflect the original structure of the multi-kinks. The sub-kink’s positions and their vibration modes provide collective coordinates that are used to construct a phenomenological model, which offers a good qualitative explanation of the observed oscillon properties. Linear radiation effects are consistently incorporated into the model, revealing their important role in the synchronization of the oscillon’s vibrational components. In contrast, oscillon decay and the sudden annihilations observed in some collisions are driven by a novel staccato-like mechanism, whereby repeated crossings of the mass threshold by the dominant frequency generate a sequence of radiation bursts.

United States

Jonathan Lozano-Mayo

Mexico

Manuel Torres-Labansat

Multi-kinks and composite oscillons in a commensurable and non degenerate double sine-Gordon model

We perform a model-independent study of new physics effects in the Higgs decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mi>γ</mi></math>, focusing on scenarios that spoil the accidental cancellation between the direct and indirect amplitudes. After imposing all existing constraints from Higgs production and decay measurements, we find that a wrong-sign <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> coupling is the only viable scenario capable of enhancing the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mi>γ</mi></math> decay width by nearly 2 orders of magnitude. Therefore, an observation of a significantly enhanced <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mi>γ</mi></math> rate at the LHC or future colliders would provide unambiguous evidence for a wrong-sign <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> coupling, directly pointing to the presence of an extended Higgs sector.

India

Portugal

Aditya Batra

South Korea

Sanjoy Mandal

Rahul Srivastava

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mi>γ</mi></math> decay: Smoking gun signature of a wrong-sign <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> coupling

In Friedmann cosmology with Einstein–Cartan torsion, the homogeneous torsion mode compatible with a separately conserved matter sector scales as $$\Phi \propto a^{-3}$$ and enters the Friedmann constraint as a stiff component of negative energy density, $$-3\Phi ^{2}\propto a^{-6}$$ . It has recently been claimed that this mode rescues the Hubble radius as an infrared cutoff for holographic dark energy, producing late-time acceleration and a phantom-divide crossing of possible relevance to DESI. We show that it cannot. With the Hubble cutoff the holographic density drops out of the deceleration parameter, and the only accelerating regime is the transient window $$\bar{a}\le a<4^{1/3}\bar{a}$$ around the torsion bounce at $$H(\bar{a})=0$$ ; placing that window at observable redshifts would force the Hubble rate to vanish in our recent past, against the measured expansion history. Requiring a viable history yields nested upper bounds on $$\Omega _{\Phi }\equiv (\Phi _{0}/H_{0})^{2}$$ : fitting the official DESI DR2 BAO likelihood gives $$\Omega _{\Phi }<8.7\times 10^{-4}$$ ( $$95\%$$ CL), the existence of a spectroscopically confirmed galaxy at $$z=14.32$$ gives $$8.4\times 10^{-5}$$ , the CMB gives $$3.1\times 10^{-10}$$ , and Big Bang nucleosynthesis gives $$5\times 10^{-24}$$ . Today’s imprint on the dark energy equation of state, $$|1+\omega _{0}|\le 2\Omega _{\Phi }/\Omega _{\Lambda }$$ , falls short of the DESI preference by two orders of magnitude at best and twenty-two at worst, and on the phantom side. In the Granda–Oliveros cutoff, torsion deepens rather than prevents the big-rip singularity. An appendix derives the Friedmann pair from the Einstein–Cartan field equations and shows that the $$a^{-3}$$ scaling is the kinematics of a diluting spin fluid; escaping the no-go requires breaking exactly that.

Chile

Fernando Izaurieta

Samuel Lepe

Cristian Quinzacara

No late-time role for adiabatic torsion: a no-go result for Hubble-cutoff holographic dark energy in Einstein–Cartan cosmology

Grand unified theories (GUTs) predict the overproduction of magnetic monopoles, leading to the so-called monopole problem, which is often addressed by cosmological inflation that dilutes their abundance. However, if inflation occurs before the GUT symmetry breaking, monopoles are produced afterwards and the problem persists. This motivates the exploration of alternative mechanisms. We propose a simple solution based on the Langacker-Pi mechanism within an $\textit{SU}$ (5) GUT framework with symmetry breaking into its special subgroup. In particular, after the gauge symmetry is broken to the Standard Model (SM) gauge group $\textit{SU}$ (3) × $\textit{SU}$ (2) × $\textit{U}$ (1) by the vacuum expectation value of an adjoint scalar, it is further broken to $\textit{SO}$(3) × $\textit{SO}$(2) . This structure is naturally realized by introducing a symmetric tensor scalar, a singlet scalar, and multiple singlet fermions. During this intermediate phase, the monopoles become connected to antimonopoles by cosmic strings, which enhances their pair annihilation and reduces their abundance. Subsequently, the symmetry is restored to the SM gauge group. The restoration transition can be either first-order or second-order, depending on the model parameters. In the case of a first-order phase transition, a stochastic gravitational-wave (GW) signal is generated. For a certain region of the parameter space, the resulting signal can lie within the sensitivity of future GW experiments.

Japan

Yu Hamada

Naoki Yamatsu

A simple solution to the monopole problem: $\textit{SU}$ (5) GUT with symmetry breaking into special subgroup

We present the design and the sensitivity reach of the qubit-based light dark matter detection experiment. We propose the novel two-chip design to reduce signal dissipation, with quantum parity measurement to enhance single-phonon detection sensitivity. We demonstrate the performance of the detector with full phonon and quasiparticle simulations. The experiment is projected to detect <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≳</mo><mn>30</mn><mtext> </mtext><mtext> </mtext><mi>meV</mi></math> energy deposition with nearly 100% efficiency and high energy resolution. The sensitivity to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>χ</mi></msub><mo>≳</mo><mn>0.01</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> dark matter scattering cross section is expected to be advanced by orders of magnitude for both light and heavy mediators, and similar improvements will be achieved for axion and dark photon absorption in the 0.04–0.2 eV mass range.

China

Xuegang Li

Yuxiang Liu

Jing Shu

Ningqiang Song

Yidong Song

Junhua Wang

Yue-Liang Wu

Tiantian Zhang

Yu-Feng Zhou

Novel light dark matter detection with a quantum parity detector using qubit arrays

This paper investigates how to extract energy from a non-Kerr rotating spacetime with an anomalous quadrupole moment via the Comisso–Asenjo magnetic reconnection mechanism. Unlike many other rotating spacetimes, this spacetime possesses closed timelike curves, and the corresponding spacetime regions must be excluded when extracting energy. After introducing the event horizon, ergosphere, and closed timelike curves of this spacetime, we deeply analyze the energy per unit enthalpy at infinity for accelerated and decelerated plasmas, the allowed region for energy extraction, and the power and efficiency of energy extraction. The results show that energy extraction is possible for both positive and negative anomalous quadrupole moments, but a positive and small anomalous quadrupole moment corresponds to higher power and efficiency of energy extraction.

Ke Wang

Xiao-Xiong Zeng

Extracting energy from a non-Kerr rotating spacetime with an anomalous quadrupole moment via magnetic reconnection

We investigate the holographic superfluid dynamics subjected to external rotation on a spherical geometry. Through a linear perturbation analysis, we identify several dynamically unstable phases in the phase diagram, each characterized by distinct unstable modes. Employing fully nonlinear numerical simulations, we further demonstrate that these unstable modes generically drive the system into vortex–antivortex configurations with definite winding numbers, determined by the symmetry of the corresponding unstable modes.