Parity violation in the early Universe holds great promise for uncovering new physics. In particular, the primordial scalar four-point correlation function is allowed to develop a parity-violating component when massive spinning particles coupled to a helical chemical potential are present during inflation. In this paper, we explore the rich physics of such a parity-violating trispectrum in the presence of a reduced speed of sound for the Goldstone boson of broken time translations. We show that this signal can be significantly large while remaining under perturbative control, offering promising observational prospects for future cosmological surveys. In the limit of a reduced sound speed, the dynamics admits an effective nonlocal description organized as a time-derivative expansion. This reveals that parity violation arises due to emergent nonlocality in the single-field effective theory. At leading order, this effective theory yields a compact trispectrum template, written in terms of elementary functions. We then conduct a comprehensive analysis of the kinematic dependence of this parity-violating trispectrum and reveal new features. In addition to the low-speed collider resonance, we find a new class of signals lying in the internal soft-limit of the correlator. This signal is characterized by an oscillatory pattern periodic in the momentum ratio, with a frequency determined by the speed of sound and the chemical potential, making it drastically distinct from the conventional cosmological collider signal.

We explore the hypothesis that the abundant presence of relativistic antimatter (positrons) in the primordial Universe is the source of the intergalactic magnetic fields we observe in the Universe today. We evaluate both Landau diamagnetic and magnetic dipole moment paramagnetic properties of the very dense primordial electron-positron $e^{+}{e}^{-}$-plasma, and obtain in quantitative terms the relatively small magnitude of the $e^{+}{e}^{-}$ magnetic moment polarization asymmetry required to produce a consistent self-magnetization in the Universe.

Models that produce axionlike particles (ALPs) after cosmological inflation due to spontaneous $U(1)$ symmetry breaking also produce cosmic-string networks. Those axionic strings lose energy through gravitational-wave emission during the whole cosmological history, generating a stochastic background of gravitational waves that spans many decades in frequency. We can therefore constrain the axion decay constant and axion mass from limits on the gravitational-wave spectrum and compatibility with dark matter abundance as well as dark radiation. We derive such limits from analyzing the most recent NANOGrav data from pulsar timing arrays (PTAs). The limits are similar to the $N_{\mathrm{eff}}$ bounds on dark radiation for ALP masses $m_a\lesssim {10}^{-22}\mathrm{eV}$. On the other hand, for heavy ALPs with $m_a\gtrsim 0.1\mathrm{GeV}$ and $N_{\mathrm{DW}}\ne 1$, new regions of parameter space can be probed by PTA data due to the dominant domain-wall contribution to the gravitational-wave background.

Recently, many works have tried to realize cosmological accelerated expansion in string theory models in the asymptotic regions of field space, with a typical scalar potential $V(\phi )$ having an exponential falloff $e^{-\gamma \phi }$. Those attempts have been plagued by the fact that $V$ is too steep, namely $\gamma \ge 2/\sqrt{d-2}$ in a $d$-dimensional spacetime. We revisit the corresponding dynamical system for arbitrary $d$ and $\gamma$ and show that for an open universe ($k=-1$) there exists a new stable fixed point $P_1$ precisely if $\gamma >2/\sqrt{d-2}$. Building on the recent work [P. Marconnet and D. Tsimpis, Universal accelerating cosmologies from 10d supergravity, J. High Energy Phys. 01 (2023) 033], we show in addition that cosmological solutions asymptoting to $P_1$ exhibit accelerated expansion in various fashions (semieternal, eternal, transient with a parametrically controlled number of $e$-folds, or roller coaster). We finally present realizations in string theory of these cosmological models with asymptotically accelerating solutions, for $d=4$ or $d=10$. We also show that these solutions do not admit a cosmological event horizon and discuss the possibility of this being a generic feature of quantum gravity.

Gravitational-wave signals from compact binary coalescences are most effectively identified by matched filter searches. These searches match the data against a pregenerated bank of gravitational-wave templates. Currently, all modeled gravitational-wave searches use templates that restrict the component spins to be aligned (or antialigned) with the orbital angular momentum. This means that they are less sensitive to gravitational-wave signals from precessing binaries, implying that a significant fraction of signals may remain undetected. In this work, we introduce a matched filter search that is sensitive to signals generated from precessing binaries. We take advantage of the fact that a gravitational-wave signal from a precessing binary can be decomposed into a power series of five harmonics. This allows us to create a generic-spin template bank that is only $\sim 3$ times larger than existing aligned-spin banks. Our new search shows a $\sim 100\%$ increase in sensitive volume for neutron star black hole binaries with total mass larger than $17.5M_{\odot }$ and in-plane spins $>0.67$, and improves sensitivity by $\sim 60\%$ on average across the full generic spin neutron-star black-hole parameter space. In addition, our generic spin search performs as well as existing aligned-spin searches for neutron star black hole signals with insignificant in-plane spins. We anticipate that this improved technique will identify significantly more gravitational-wave signals and help shed light on the unknown spin distribution of binaries in the Universe.

We have attempted to mitigate the challenge of connecting the neutron star (NS) properties with the nuclear matter parameters that describe equations of state (EOSs). The efforts to correlate various neutron star properties with individual nuclear matter parameters have been inconclusive. A principal component analysis is employed as a tool to uncover the connection between multiple nuclear matter parameters and the tidal deformability as well as the radius of neutron stars within the mass range of $1.2–1.8M_{\odot }$. The essential EOSs for neutron star matter at low densities have been derived using both uncorrelated uniform distributions and minimally constrained joint-posterior distributions of nuclear matter parameters. For higher densities ($\rho >0.32{\mathrm{fm}}^{-3}$), the EOSs have been established through a suitable parametrization of the speed of sound, which consistently maintains causality and gradually approaches the conformal limit. Our analysis reveals that in order to account for over 90% of the variability in NS properties, it is crucial to consider two or more principal components, emphasizing the significance of employing multivariate analysis. To explain the variability in tidal deformability needs a greater number of principal components compared to those for the radius at a given NS mass. The contributions from isovector nuclear matter parameters to the tidal deformability and radius of NS decrease by $\sim 25\%$ with the increase in mass of NS from $1.2M_{\odot }$ to $1.8M_{\odot }$.

Interband transitions of electrons in a gapped graphene monolayer are highly stimulated near the Fermi surface when a high-frequency electric wave of weak intensity and a strong constant electric field are superposed in the plane of the flake. We consider this phenomenon equivalent to the Franz-Keldysh effect, paying particular attention to the regime where the photon energy linked to the fast-oscillating field is just below the graphene gap, so that the quantum transitions still occur through tunneling effects while being facilitated by the one-photon absorption channel. In the considered parameter regime the photocatalyzed current linked to the described setup is shown to exceed the one driven by the strong field solely by several orders of magnitude. Conditions to relieve the impact of the field’s finite extension are discussed, and a formula for the residual current density is derived. The robustness of our assessment supports the viability of detecting this phenomenon in graphene, thus providing a simulation of the dynamically-assisted Schwinger mechanism in QED.

Direct searches for dark matter with large-scale noble liquid detectors have become sensitive enough to detect the coherent scattering of local neutrinos. This will become a very challenging background to dark matter discovery in planned future detectors. For dark matter with mass above 10 GeV, the dominant neutrino backgrounds on Earth are atmospheric neutrinos created by cosmic ray collisions with the atmosphere. In contrast, the Moon has almost no atmosphere and nearly all cosmic rays incident on the Moon first collide with the lunar surface, producing a very different neutrino spectrum. In this work we estimate the total flux and spectrum of neutrinos near the surface of the Moon. We then use this to show that a large-scale liquid xenon or argon detector located on the Moon could potentially have significantly greater sensitivity to dark matter compared to an equivalent detector on Earth due to effectively reduced neutrino backgrounds.

We examine $W$ and $Z$ boson pair production processes at electron-positron collider experiments in the $SU(3{)}_C\times SO(5{)}_W\times U(1{)}_X$ gauge-Higgs unification (GHU) model. We find that the deviation of the total cross section for the $e^{-}{e}^{+}\to W^{-}{W}^{+}$ process from the Standard Model (SM) in the GHU model with parameter sets, which are consistent with the current experiments, is about 0.5% to 1.5% and 0.6% to 2.2% for $\sqrt{s}=250\mathrm{GeV}$ and 500 GeV, respectively, depending on the initial electron and positron polarization. We find that for the $e^{-}{e}^{+}\to ZZ$ process the deviation from the SM in the GHU model is at most 1%. We find that unitarity bound for the $e^{-}{e}^{+}\to W^{-}{W}^{+}$ process is satisfied in the GHU model as in the SM, as a consequence of the relationship among coupling constants.

In this article, we review and update implications of the muon anomalous magnetic moment (muon $g-2$) anomaly for two-Higgs-doublet models (2HDMs), which are classified according to imposed symmetries and their resulting Yukawa sector. In the minimal setup, the muon $g-2$ anomaly can be accommodated by the type-X (leptophilic) 2HDM, flavor-aligned 2HDM (FA2HDM), muon-specific 2HDM ($\mu 2\mathrm{HDM}$), and $\mu \tau$-flavor-violating 2HDM. We summarize all relevant experimental constraints from high-energy collider experiments and flavor experiments, as well as the theoretical constraints from the perturbative unitarity and vacuum stability bounds, to these 2HDMs in light of the muon $g-2$ anomaly. We clarify the available parameter spaces of these 2HDMs and investigate how to probe the remaining parameter regions in future experiments. In particular, we find that, due to the updated $B_s\to {\mu }^{+}{\mu }^{-}$ measurement, the remaining parameter region of the FA2HDM is almost equivalent to the one of the type-X 2HDM. Furthermore, based on collider simulations, we find that the type-X 2HDM is excluded and the $\mu 2\mathrm{HDM}$ scenario will be covered with the upcoming run 3 data.

In the composite Higgs model the Higgs field arises as the pseudo-Goldstone mode, which is associated with a dynamical symmetry breaking in a new strongly coupled sector. We present a soft-wall holographic model where such symmetry breaking occurs as a first order phase transition. In this case the bubble nucleation in the early universe becomes possible. To study the homogeneous solutions in the models of this type we present the perturbation theory approach. We estimate the gravitational wave spectrum produced during the nucleation phase and find it to be detectable with the planned gravitational wave detectors.

Motivated by the recent measurement of muon anomalous magnetic moment at Fermilab, the rapid progress of the LHC search for supersymmetry, and the significantly improved sensitivities of dark matter direct detection experiments, we studied their impacts on the minimal supersymmetric standard model (MSSM). We conclude that higgsino mass should be larger than about 500 GeV for $M_1<0$ and 630 GeV for $M_1>100\mathrm{GeV}$, where $M_1$ denotes the bino mass. These improved bounds imply a tuning of $\mathcal{O}(1\%)$ to predict the $Z$-boson mass and simultaneously worsen the naturalness of the $Z$- and $h$-mediated resonant annihilations to achieve the measured dark matter density. We also conclude that the LHC restrictions have set lower bounds on the sparticle mass spectra: $m_{{\tilde{\chi }}_1^0}\gtrsim 210\mathrm{GeV}$, $m_{{\tilde{\chi }}_2^0},m_{{\tilde{\chi }}_1^{\pm }}\gtrsim 235\mathrm{GeV}$, $m_{{\tilde{\chi }}_3^0}\gtrsim 515\mathrm{GeV}$, $m_{{\tilde{\chi }}_4^0}\gtrsim 525\mathrm{GeV}$, $m_{{\tilde{\chi }}_2^{\pm }}\gtrsim 530\mathrm{GeV}$, $m_{{\tilde{\nu }}_{\mu }}\gtrsim 235\mathrm{GeV}$, $m_{{\tilde{\mu }}_1}\gtrsim 215\mathrm{GeV}$, and $m_{{\tilde{\mu }}_2}\gtrsim 250\mathrm{GeV}$, where ${\tilde{\chi }}_2^0$ and ${\tilde{\chi }}_1^{\pm }$ are wino-dominated when they are lighter than about 500 GeV. These bounds are far beyond the reach of the LEP experiments in searching for supersymmetry and have not been acquired before. In addition, we illuminate how some parameter spaces of the MSSM have been tested at the LHC and provide five scenarios in which the theory coincides with the LHC restrictions. Once the muon $g\text{−}2$ anomaly is confirmed to originate from supersymmetry, this research may serve as a guide to explore the characteristics of the MSSM in future experiments.

We consider the dipole portal to sterile neutrinos, also called heavy neutral leptons (HNLs). The dipole interaction with the photon leads to HNL production in meson decays as well as triggers the HNL decay into an active neutrino and a photon. HNLs with masses of the order of 0.01–1 GeV are naturally long lived if the dipole coupling is sufficiently small. We perform Monte Carlo simulations and derive the sensitivities of the proposed FASER2 and FACET long-lived particle experiments to HNLs produced via the dipole operator in meson decays at the high-luminosity LHC. Our findings show that these future detectors will be complementary to each other, as well as to existing experiments, and will be able to probe new parts of the parameter space, especially in the case of the dipole operator coupled to the tau neutrino.

A variety of supergravity and string models involve hidden sectors where the hidden sectors may couple feebly with the visible sectors via a variety of portals. While the coupling of the hidden sector to the visible sector is feeble, its coupling to the inflaton is largely unknown. It could couple feebly or with the same strength as the visible sector, which would result in either a cold or a hot hidden sector at the end of reheating. These two possibilities could lead to significantly different outcomes for observables. We investigate the thermal evolution of the two sectors in a cosmologically consistent hidden sector dark matter model where the hidden sector and the visible sector are thermally coupled. Within this framework, we analyze several phenomena to illustrate their dependence on the initial conditions. These include the allowed parameter space of models, dark matter relic density, proton-dark matter cross section, effective massless neutrino species at big bang nucleosynthesis time, self-interacting dark matter cross section, where self-interaction occurs via exchange of dark photon, and Sommerfeld enhancement. Finally, fits to the velocity dependence of dark matter cross sections from galaxy scales to the scale of galaxy clusters is given. The analysis indicates significant effects of the initial conditions on the observables listed above. The analysis is carried out within the framework where dark matter is constituted of dark fermions, and the mediation between the visible and the hidden sector occurs via the exchange of dark photons. The techniques discussed here may have applications for a wider class of hidden sector models using different mediations between the visible and the hidden sectors to explore the impact of big bang initial conditions on observable physics.

We analyze the world polarized deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data at low values of $x<0.1$, using small-$x$ evolution equations for the flavor singlet and nonsinglet helicity parton distribution functions (hPDFs), which resum all powers of both ${\alpha }_s{\ln }^2(1/x)$ and ${\alpha }_s\ln (1/x)\ln (Q^2/Q_0^2)$, with ${\alpha }_s$ being the strong coupling constant. The hPDFs for quarks, antiquarks, and gluons are extracted and evolved to lower values of $x$ to make predictions for the future Electron-Ion Collider (EIC). We improve on our earlier work by employing the more realistic large-$N_c\&N_f$ limit of the revised small-$x$ helicity evolution, and by incorporating running coupling corrections along with SIDIS data into the fit. We find an anticorrelation between the signs of the gluon and $C$-even quark hPDFs, as well as the $g_1$ structure function. While the existing low-$x$ polarized DIS and SIDIS data are insufficient to constrain the initial conditions for the polarized dipole amplitudes in the helicity evolution equations, future EIC data will allow more precise predictions for hPDFs and the $g_1$ structure function for $x$ values beyond those probed at the EIC. Using the obtained hPDFs, we discuss the contributions to the proton spin from quark and gluon spins at small $x$.