The Laser Interferometer Space Antenna (LISA) is poised to revolutionize astrophysics and cosmology in the late 2030s by unlocking unprecedented insights into the most energetic and elusive astrophysical phenomena. The mission envisages three spacecraft, each equipped with two lasers, on a triangular constellation with 2.5 million-kilometer arm-lengths. Six interspacecraft laser links are established on a laser-transponder configuration, where five of the six lasers are offset phase locked to another. The need to determine a suitable set of transponder offset frequencies precisely, given the constraints imposed by the onboard metrology instrument and the orbital dynamics, poses an interesting technical challenge. In this paper we describe an algorithm that solves this problem via quadratic programming. The algorithm can produce concrete frequency plans for a given orbit and transponder configuration, ensuring that all of the critical interferometric signals stay within the desired frequency range throughout the mission lifetime, and enabling LISA to operate in science mode uninterruptedly.

We show that the QCD axion couples to the electromagnetic kinetic term at one loop. The result is that if axions make up dark matter, they induce temporal variation of the fine structure constant $\alpha$, which is severely constrained. We recast these constraints on the QCD axion parameter space. We also discuss how to generalize our finding to axionlike particles, and the resulting constraints.

In proton-proton and heavy-ion collisions, the study of charm hadrons plays a pivotal role in understanding the QCD medium and provides an undisputed testing ground for the theory of strong interaction, as they are mostly produced in the early stages of collisions via hard partonic interactions. The lightest open charm, $D^0$ meson ($c\overline{u}$), can originate from two separate sources. The prompt $D^0$ originates from either direct charm production or the decay of excited open charm states, while the nonprompt stems from the decay of beauty hadrons. In this paper, using different machine learning (ML) algorithms such as XGBoost, CatBoost, and Random Forest, an attempt has been made to segregate the prompt and nonprompt production modes of the $D^0$ meson signal from its background. The ML models are trained using the invariant mass through its hadronic decay channel, i.e., $D^0\to {\pi }^{+}{K}^{-}$, pseudoproper time, pseudoproper decay length, and distance of closest approach of $D^0$ meson, using pythia8 simulated $pp$ collisions at $\sqrt{s}=13\mathrm{TeV}$. The ML models used in this analysis are found to retain the pseudorapidity, transverse momentum, and collision energy dependence. In addition, we report the ratio of nonprompt to prompt $D^0$ yield, the self-normalized yield of prompt and nonprompt $D^0$, and explore the charmonium, $J/\psi$ to open charm, $D^0$ yield ratio as a function of transverse momenta and normalized multiplicity. The observables studied in this paper are well predicted by all the ML models compared to the simulation.

The emergence of the Efimov effect in the $D^{*}{D}^{*}{D}^{*}$ system is explored under the assumption that the heavy partner of the $T_{cc}^{+}$ exists as a $D^{*}{D}^{*}$ molecule with $(I)J^P=(0)1^{+}$. The three-to-three relativistic scattering amplitude is obtained from the ladder amplitude formalism, built from an energy-dependent contact two-body potential where the molecular component of the $T_{cc}^{*}$ state can be varied. We find that $(I)J^P=(\frac{1}{2})0^{-}$ three-body bound states can be formed, with properties that suggest that the Efimov effect can be realized for reasonable values of the molecular probability and binding energy of the $T_{cc}^{*}$.

Measuring the energy loss and mass of highly ionizing particles predicted by theories from beyond the Standard Model poses considerable challenges to conventional detection techniques. Such particles are predicted to experience energy loss to matter they pass through that exceeds the dynamic range specified for most readout chips, leading to saturation of the detectors’ electronics. Consequently, achieving precise energy loss and mass measurements becomes unattainable. We present a new approach to detect such highly ionizing particles using time projection chambers that overcomes this limitation and provides a case study for triggering on magnetic monopoles.

We construct Carroll-invariant theories with fields propagating outside the Carroll light cone, i.e., at a speed strictly greater than zero (“Carroll swiftons”). We first consider models in flat Carroll spacetime in general dimensions, where we present scalar and vector Carroll swifton field theories. We then turn to the coupling to gravity and achieve in particular in two dimensions a Carroll-invariant scalar swifton by coupling it suitably to Carroll dilaton gravity. Its backreaction on the geometry generates dynamical torsion.

We describe a simple dark sector structure which, if present, has implications for the direct detection of dark matter (DM); the dark sink. A dark sink transports energy density from the DM into light dark-sector states that do not appreciably contribute to the DM density. As an example, we consider a light, neutral fermion $\psi$ which interacts solely with DM $\chi$ via the exchange of a heavy scalar $\mathrm{\Phi }$. We illustrate the impact of a dark sink by adding one to a DM freeze-in model in which $\chi$ couples to a light dark photon ${\gamma }^{\prime }$ which kinetically mixes with the Standard Model (SM) photon. This freeze-in model (absent the sink) is itself a benchmark for ongoing experiments. In some cases, the literature for this benchmark has contained errors; we correct the predictions and provide them as a public code. We then analyze how the dark sink modifies this benchmark, solving coupled Boltzmann equations for the dark-sector energy density and DM yield. We check the contribution of the dark sink $\psi$’s to dark radiation; consistency with existing data limits the maximum attainable cross section. For DM with a mass between $\mathrm{MeV}-\mathcal{O}(10\mathrm{GeV})$, adding the dark sink can increase predictions for the direct detection cross section all the way up to the current limits.

We consider a ${\mathbb{Z}}_3$ gauge theory coupled to three degenerate massive flavors of fermions, which we term Quantum Z(3) Dynamics, QZD. The spectrum can be computed in $1+1$ dimensions using tensor networks. In weak coupling the spectrum is that of the expected mesons and baryons, although the corrections in weak coupling are nontrivial, analogous to those of nonrelativistic QED in $1+1$ dimensions. In strong coupling, besides the usual baryon, the singlet meson is a baryon-antibaryon state. For two special values of the coupling constant, the lightest baryon is degenerate with the lightest octet meson, and the lightest singlet meson, respectively.

We consider null and timelike geodesics around a spherically symmetric, nonrotating coherent quantum black hole (CQBH). The classical limit of the geometry of a CQBH departs from that of the Schwarzschild spacetime at short scales and depends on one parameter $R_s$ which can be interpreted as the physical radius of the “quantum” core. We study circular orbits, photon rings, and lensing effects and compare them with the Schwarzschild metric. Using the relativistic ray-tracing code gyoto, we produce a simulation of the shadow and show that thin accretion disks around a CQBH possess unique ring structures that distinguish them from other theoretical models.

We propose a scenario that can explain the early-time inflation and the late-time dark energy within a unified framework. A scalar potential combining power-law and exponential type in a context of extended Jordan-Brans-Dicke gravity is critically important for this realization. A realistic scenario can be achieved in a two-field model in which one directional motion in field space realizes the slow-roll inflation. The inflaton ends up with oscillatory period and turns its direction to another direction that is identified as the quintessence field, giving rise to the dark energy at late times. The inflaton oscillation is expected to realize efficient heating if parametric amplification works. Along the quintessence direction, the present universe is on the way to reach the asymptotic fixed point. We search for a successful parameter region, taking the potential function in the form of low-order field powers times decreasing exponential in two-dimensional field space.

Axion-like particles (ALPs) are a well-motivated dark matter candidate that solves some of the problems in the clustering of large scale structure in cosmology. ALPs are often described by a simplified quadratic potential to specify the dynamics of the axion field and are included in cosmological analysis codes using a modified fluid prescription. In this paper, we consider the extreme axion: a version of the axion with a high initial field angle that produces an enhancement (rather than a suppression) of structure on small scales around the Jeans length, which can be probed by measurements of clustering such as the extended Baryonic Oscillation Spectroscopic Survey (eBOSS) DR14 Lyman-$\alpha$ (Ly-$\alpha$) forest. We present a novel method of modeling the extreme axion as a cosmological fluid, combining the generalized dark matter model with the effective fluid approach presented in the axionCAMB software as well as implementing a series of computational innovations to efficiently simulate the extreme axions. We find that, for axion masses between ${10}^{-23}\mathrm{eV}\lesssim m_{\mathrm{ax}}\lesssim {10}^{-22.5}\mathrm{eV}$, constraints on the axion fraction imposed by the eBOSS DR14 Ly-$\alpha$ forest can be significantly weakened by allowing them to be in the form of extreme axions with a starting angle between $\pi -{10}^{-1}\lesssim {\theta }_i\lesssim \pi -{10}^{-2}$. This work motivates and enables a more robust hydrodynamical analysis of extreme axions in order to compare them to high-resolution Ly-$\alpha$ forest data in the future.

Embedded walls are domain wall solutions which are unstable in the vacuum but stabilized in a plasma of the early Universe. We show how embedded walls in which the electroweak symmetry is restored can lead to an efficient scenario of electroweak baryogenesis. We construct an extension of the Standard Model of particle physics in which embedded walls exist and are stabilized in an electromagnetic plasma.

At high energies, the dynamics of a plasma with charged fermions can be described in terms of chiral magnetohydrodynamics. Using direct numerical simulations, we demonstrate that chiral magnetic waves (CMWs) can produce a chiral asymmetry ${\mu }_5={\mu }_{\mathrm{L}}-{\mu }_{\mathrm{R}}$ from a spatially fluctuating (inhomogeneous) chemical potential $\mu ={\mu }_{\mathrm{L}}+{\mu }_{\mathrm{R}}$, where ${\mu }_{\mathrm{L}}$ and ${\mu }_{\mathrm{R}}$ are the chemical potentials of left- and right-handed electrically charged fermions, respectively. If the frequency of the CMW is less than or comparable to the characteristic growth rate of the chiral dynamo instability, the magnetic field can be amplified on small spatial scales. The growth rate of this small-scale chiral dynamo instability is determined by the spatial maximum value of ${\mu }_5$ fluctuations. Therefore, the magnetic field amplification occurs during periods when ${\mu }_5$ reaches temporal maxima during the CMW. If the small-scale chiral dynamo instability leads to a magnetic field strength that exceeds a critical value, which depends on the resistivity and the initial value of $\mu$, magnetically dominated turbulence is produced. Turbulence gives rise to a large-scale dynamo instability, which we find to be caused by the magnetic alpha effect. Our results have consequences for the dynamics of certain high-energy plasmas, such as the early Universe.

Cosmological first-order phase transitions (1stOPTs) are said to be strongly supercooled when the nucleation temperature is much smaller than the critical temperature. These are often encountered in theories that admit a nearly scale-invariant potential, for which the bounce action decreases only logarithmically with temperature. During supercooled 1stOPTs the equation of state of the universe undergoes a rapid and drastic change, transitioning from vacuum domination to radiation domination. The statistical variations in bubble nucleation histories imply that distinct causal patches percolate at slightly different times. Patches which percolate the latest undergo the longest vacuum-domination stage and as a consequence develop large overdensities triggering their collapse into primordial black holes (PBHs). We derive an analytical approximation for the probability of a patch to collapse into a PBH as a function of the 1stOPT duration, ${\beta }^{-1}$, and deduce the expected PBH abundance. We find that 1stOPTs which take more than 15% of a Hubble time to complete ($\beta /H\lesssim 7$) produce observable PBHs. Their abundance is independent of the duration of the supercooling phase, in agreement with the de Sitter no hair conjecture.

In this paper, we investigate the effect of the string radius of curvature $R_{\text{Gaussian}}$ on the massive and massless scalar radiation emitted from collisions of traveling waves propagating along an axion (global cosmic) string. We construct initial conditions for two colliding Gaussians and perform parameter scans over their amplitude $A$ and standard deviation ${\sigma }_{\mathrm{d}}$. We show that these collisions emit isotropic bursts of massless radiation and that the energy emitted via this channel obeys a power law $\stackrel{\propto }{\sim }{A}^{\gamma }$, where the coefficient $\gamma$ depends on the regime of $A/\delta$ and $\delta$ is the string width. Massive radiation is exponentially suppressed $\stackrel{\propto }{\sim }{e}^{-\zeta R_{\text{Gaussian}}}$ in the quasilinear regime ${\sigma }_{\mathrm{d}}\gg \delta$ and exhibits power-law decay $\stackrel{\propto }{\sim }{R}_{\text{Gaussian}}^{-{\gamma }^{\prime }}$ in the nonlinear regime ${\sigma }_{\mathrm{d}}\lesssim 2\delta$, with different $\zeta$ and ${\gamma }^{\prime }$ in different regimes of $R_{\text{Gaussian}}$. In this nonlinear regime, massive particle radiation can comprise up to 50% of the total energy emitted. Drawing on a known parallel between axion radiation from global strings and gravitational radiation from Abelian-Higgs strings, this suggests that massive particle radiation may become significant with respect to the massless (gravitational) channel for such nonlinear burst signals. For all configurations studied, we obtain a spectral index $q\gtrsim 1$ for the axion radiation, where $q\to 1$ as $A$ increases; i.e., a higher proportion of radiation is emitted in high-frequency modes.

Wavelike, bosonic dark matter candidates like axions and dark photons can be detected using microwave cavities known as haloscopes. Traditionally, haloscopes consist of tunable copper cavities operating in the ${\mathrm{TM}}_{010}$ mode, but ohmic losses have limited their performance. In contrast, superconducting radio frequency (SRF) cavities can achieve quality factors of $\sim {10}^{10}$, perhaps 5 orders of magnitude better than copper cavities, leading to more sensitive dark matter detectors. In this paper, we first derive that the scan rate of a haloscope experiment is proportional to the loaded quality factor $Q_{\mathrm{L}}$, even if the cavity bandwidth is much narrower than the dark matter halo line shape. We then present a proof-of-concept search for dark photon dark matter using a nontunable ultrahigh-quality SRF cavity. We exclude dark photon dark matter with kinetic mixing strengths of $\chi >1.5\times {10}^{-16}$ for a dark photon mass of $m_{A^{\prime }}=5.35\mathrm{\mu }\mathrm{eV}$, achieving the deepest exclusion to wavelike dark photons by almost an order of magnitude.

The light dark matter mass regime has emerged as the next frontier in the direct detection experiment due to the lack of any detection signal in the higher mass range. In this paper, we propose a new detector material, a bilayer stack of graphene to detect sub-MeV dark matter. Its voltage-tunable low energy sub-eV electronic band gap makes it an excellent choice for the detector material of a light dark matter search experiment. We compute its dielectric function using the random phase approximation and estimate the projected sensitivity for sub-MeV dark matter-electron scattering and sub-eV dark matter absorption. We show that a bilayer graphene dark matter detector can have competitive sensitivity as other candidate target materials, like a superconductor, but with a tunable threshold energy in this mass regime. The dark matter scattering rate in bilayer graphene is also characterized by a daily modulation from the rotation of the Earth which may help us mitigate the backgrounds in a future experiment. We also outline a detector design concept and provide noise estimates that can be followed to set up an experiment in the future.

In this paper, we explore the phenomenology of massive axionlike particles (ALPs) coupled to quarks and gluons, dubbed “QCD ALPs,” with an emphasis on the associated low-energy observables. ALPs coupled to gluons and quarks not only induce nuclear interactions at scales below the QCD scale, relevant for ALP production in supernovae (SNe), but naturally also couple to photons similarly to the QCD axion. We discuss the link between the high-energy formulation of ALP theories and their effective couplings with nucleons and photons. The induced photon coupling allows ALPs with masses $m_a\gtrsim 1\mathrm{MeV}$ to efficiently decay into photons, and astrophysical observables severely constrain the ALP parameter space. We show that a combination of arguments related to SN events rule out ALP-nucleon couplings down to $g_{aN}\gtrsim {10}^{-11}–{10}^{-10}$ for $m_a\gtrsim 1\mathrm{MeV}$—a region of the parameter space that was hitherto unconstrained.

We implement an eccentric search for compact binary mergers based on particle swarm optimization. Orbital eccentricity is an invaluable input for understanding the formation scenarios of the binary mergers and can play a pivotal role in finding their electromagnetic counterparts. Current modeled searches rely on precomputed template banks that are computationally expensive and resistant toward expanding the search parameter space dimensionality. On the other hand, particle swarm optimization offers a straightforward algorithm that dynamically selects template points while exploring an arbitrary dimensional parameter space. Through extensive evaluation using simulated signals from spin-aligned eccentric binary mergers, we discovered that the search exhibits a remarkable autonomy in capturing the effects of both eccentricity and spin. We describe our search pipeline and revisit some of the merger candidates from the gravitational wave transient catalogs.

We present a coupled channel treatment of meson-meson dynamics, for systems with spin-parity $1^{+}$, and determine the corresponding amplitudes by solving the Bethe-Salpeter equations, which lead to the generation of two axial resonances when mesons are considered as the degrees of freedom in the model. One of them is narrow and has properties in good agreement with those of $D_1(2420)$. The other pole is wider, but its real and imaginary parts do not match well with the mass and width of $D_1(2430)$. The situation improves when a bare quark-model state is included, indicating that the dynamics at the quark level as well as among hadrons can describe the two states simultaneously. Further, we discuss that there exists a divergence in the value of the $D^{*}\pi$ scattering length determined through data coming from lattice QCD calculations and from heavy ion collisions. Such different values can be accommodated in the model by making small changes in the parameters while producing two poles having properties compatible with the two lightest $D_1$ states. With these results, we proceed to calculate the correlation function for the $D^{*+(0)}{\pi }^{0(+)}$ system for different sizes of the source. We discuss which scenarios can be useful to shed some light on the issue.