Deuterons are the most abundant secondary cosmic ray species in the Galaxy, but their study has been severely limited due to experimental challenges. In an era with new experiments and high-precision measurements in cosmic rays, having a low-uncertainty deuteron flux in a wide energy range becomes possible. The deuteron-over-helium ratio ($d/{}^4\mathrm{He}$) is important to understand the propagation of cosmic rays in the Galaxy and in the heliosphere, complementing observations with heavier nuclei like the boron-to-carbon ratio. In this work, the most up-to-date results of the deuteron flux and the $d/{}^4\mathrm{He}$ ratio at the top of the atmosphere have been obtained using galprop and a 3D solar modulation model. It was found that the simulation describes the deuteron flux and $d/{}^4\mathrm{He}$ data below $1\mathrm{GeV}/n$ within the uncertainties of the model. However, the model underestimates the best-published measurements available at high energy. This discrepancy suggests different effective diffusions have to be considered between secondary light species like deuterons and heavier nuclei. Either this is a consequence of a break in the universality of propagation between light and heavier nuclei or a lack of precision measurements, it is something AMS-02 will help to resolve in the near future.

Binary black holes may form and merge dynamically. These binaries are likely to become bound with high eccentricities, resulting in a burst of gravitational radiation at their point of closest approach. When such a binary is perturbed by a third body, the evolution of the orbit is affected, and gravitational-wave burst times are altered. The bursts times therefore encode information about the tertiary. In order to extract this information, we require a prescription for the relationship between the tertiary properties and the gravitational-wave burst times. In this paper, we demonstrate a toy model for the burst times of a secular three-body system. We show how Bayesian inference can be employed to deduce the tertiary properties when the bursts are detected by next-generation ground-based gravitational-wave detectors. We study the bursts from an eccentric binary with a total mass of $60M_{\odot }$ orbiting an $6\times {10}^8{M}_{\odot }$ supermassive black hole. When we assume no knowledge of the eccentric binary, we are unable to tightly constrain the existence or properties of the tertiary, and we recover biased posterior probability distributions for the parameters of the eccentric binary. However, when the properties of the binary are already well known—as is likely if the late inspiral and merger are also detected—we are able to more accurately infer the mass of the perturber, $m_3$, and its distance from the binary, $R$. When we assume measurement precision on the binary parameters consistent with expectations for next-generation gravitational-wave detectors, we can be greater than 90% confident that the binary is perturbed. When the orbit of the binary around the tertiary is face-on with respect to the observer, there are large statistical uncertainties on the recovered tertiary properties ($m_3$, $R_3$, and orbital phase descriptors ${\omega }_0$ and $V_{3,0}$) due to correlations between these parameters in the simple toy model. However, if the orbit is tilted away from face-on, these uncertainties can be substantially reduced. Future models allowing for nonsecular evolution may further decrease measurement uncertainties by breaking more correlations between binary and tertiary parameters.

We report on a systematic study on the entanglement between helicity degrees of freedom generated at tree level in quantum electrodynamics two-particle scattering processes. We determine the necessary and sufficient dynamical conditions for outgoing particles to be entangled with one another, and expose the hitherto unknown generation of maximal or nearly maximal entanglement through Bhabha and Compton scattering. Our work is an early step in revisiting quantum field theory and high-energy physics in the light of quantum information theory.

In Wigner function approach with relaxation time approximation, we calculate electric and magnetic conductivities of a fermion system in the strong magnetic field. The linear response has been calculated to the perturbation of electromagnetic fields on the background constant magnetic field. The Wigner function is separated into an equilibrium part in the background magnetic field and an off-equilibrium part induced by perturbative fields. The analytical expression for the equilibrium part and the corresponding equilibrium conditions are given. For the off-equilibrium part, we obtain the kinetic equation at the leading order in $\hslash$ from the master equation of the Wigner function. When perturbative fields only depend on the proper time, the off-equilibrium part can be analytically solved, from which the vector and axial vector currents are obtained. We obtain the longitudinal and transverse Ohm conductivities as well as Hall conductivity as the linear response of the vector current to the perturbative electric field. The behaviors of these conductivities as functions of the evolving time, relaxation time, particle mass, and strength of the background magnetic field are investigated both analytically and numerically.

In a singlet pseudoscalar extension of the two-Higgs-doublet model, we discuss spontaneous $CP$ violation electroweak baryogenesis via two different patterns of phase transitions (PTs): (i) two-step PTs whose first step and second step are strongly first order; (ii) three-step PTs whose first step is second order and the second step and third step are strongly first order. For the case of the two-step pattern, the first-step PT takes place at a high temperature, converting the origin phase into an electroweak symmetry-broken phase and breaking the $CP$ symmetry spontaneously. Thus, the baryon number is produced during the first-step PT. At the second-step PT, the phase is converted into the observed vacuum at zero temperature, and the $CP$ symmetry is restored. In both phases, the sphaleron processes are sufficiently suppressed, which keep the baryon number unchanged. For the case of the three-step PTs, the pseudoscalar field first acquires a nonzero vacuum expectation value (VEV), and VEVs of other fields still remain zero during the first-step PT. The following PTs and electroweak baryogenesis are similar to the case of the two-step PTs. In addition, the gravitational wave spectra can have one or two peaks through the two-step and the three-step PTs, and we discuss the detectability at the future gravitational wave detectors.

Large classes of nonsupersymmetric string models equipped with standard-model features have been constructed, but very little of their phenomenology is known. Interestingly, their spectra exhibit scalar fields whose only couplings to observed particles is through a multi-Higgs sector. On the other hand, bottom-up models with Higgs portals offer still an acceptable framework for dark matter. We explore realizations of such Higgs portals in promising heterotic orbifold models without supersymmetry. We find that a sample model includes Higgs vacua that are stable at one-loop, in which the Higgs sector is compatible with particle-physics observations and a scalar can account for the measured dark matter abundance. In such vacua, interesting constraints on the masses of the dark matter candidate and the heavy Higgs sector are uncovered. These compelling results are not limited to string models, as they can be embedded in similarly motivated bottom-up schemes.

In this work, we explore in detail the presence of scalar resonances in the $WW$ fusion process in the context of the LHC experiments working in the theoretical framework provided by Higgs effective field theories (HEFTs). While the phenomenology of vector resonances is reasonably understood in the framework of Weinberg sum-rules and unitarization studies, scalar resonances are a lot less constrained and, more importantly, do depend on HEFT low-energy effective couplings different from the ones of vector resonances that are difficult to constrain experimentally. More specifically, unitarization techniques combined with the requirement of causality allows us to set nontrivial bounds on Higgs self-interactions. This is due to the need for considering coupled channels in the scalar case along the unitarization process. As a byproduct, we can gain some relevant information on the Higgs sector from $WW\to WW$ elastic processes without needing to consider two-Higgs production.

Efficient digitization is required for quantum simulations of gauge theories. Schemes based on discrete subgroups use a smaller, fixed number of qubits at the cost of systematic errors. We systematize this approach by deriving the single plaquette action through matching the continuous group action to that of a discrete one via group character expansions modulo the field fluctuation contributions. We accompany this scheme by simulations of pure gauge over the largest discrete crystal-like subgroup of $SU(3)$ up to the fifth order in the coupling constant.

We investigate the two-gluon-exchange model of the Pomeron using nonperturbative gluon propagators characterized by a dynamical mass scale. We present the results for an analysis of the available $pp$ differential cross section data at TeV energies which accounts for dynamical gluon masses obtained from a nonlinear version of the Schwinger-Dyson equations. We show that our two-gluon exchange model gives an excellent description of the LHC data, provided we demand the Reggeization of the scattering amplitude and make a suitable choice for the convolution of proton wave functions.

We investigate the in-medium properties of pseudoscalar and vector mesons with the light-light and heavy-light quarks in a light-front quark model, using the in-medium quark properties computed by the quark-meson coupling model. Both models are constructed on an equal footing with the constituent quark degree of freedom. Here, we particularly focus on the weak decay constants and distribution amplitudes (DAs) of the mesons in symmetric nuclear matter. We find that the weak decay constants decrease as nuclear density increases for $\pi$, $K$, $D$, and $B$ pseudoscalar as well as $\rho$, $K^{*}$, $D^{*}$, and $B^{*}$ vector mesons, where their properties in free space have good agreement with the available experimental and lattice QCD data. A larger reduction is found for the light-light quark pseudoscalar mesons, while a smaller reduction is found for the heavy-light quark vector mesons, in particular, with the bottom quark. We discuss the effect of the vector potential on the weak decay constants, and present our predictions for the in-medium modifications of DAs. Also, a comparison with the free space lattice QCD data is made.

Einstein-Gauss-Bonnet gravity in high-dimensional spacetime is intriguing. Here, the properties of thick branes generated by a bulk scalar field in the five-dimensional Einstein-Gauss-Bonnet gravity were studied. With the help of the superpotential method, we obtain a series of multikink brane solutions. We also analyze the linear stability of the brane system under tensor perturbations and prove that they are stable. The massless graviton is shown to be localized near the brane and hence the four-dimensional Newtonian potential can be recovered. By comparing the properties of these thick branes under different superpotentials we find with some specific choice of superpotential the Gauss-Bonnet term can determine the scalar field are multikink or single kink.

We model the scalar waves produced during the ringdown stage of binary black hole coalescence in Einstein-scalar-Gauss-Bonnet (EsGB) gravity, using numerical relativity simulations of the theory in the decoupling limit. Through a conformal coupling of the scalar field to the metric in the matter-field action, we show that the gravitational waves in this theory can have a scalar polarization. We model the scalar quasinormal modes of the ringdown signal in EsGB gravity, and quantify the extent to which current and future gravitational wave detectors could observe the spectrum of scalar radiation emitted during the ringdown phase of binary black hole coalescence. We find that within the limits of the theory’s coupling parameters set by current theoretical and observational constraints, the scalar ringdown signal from black hole remnants in the ${10}^1–{10}^3{M}_{\odot }$ mass range is expected to be well below the detectability threshold with the current network of gravitational-wave detectors (LIGO-Virgo-KAGRA), but is potentially measurable with next-generation detectors such as the Einstein Telescope.

Gravitational waves provide us with an extraordinary tool to study the matter inside neutron stars. In particular, the postmerger signal probes an extreme temperature and density regime and will help reveal information about the equation of state of supranuclear-dense matter. Although current detectors are most sensitive to the signal emitted by binary neutron stars before the merger, the upgrades of existing detectors and the construction of the next generation of detectors will make postmerger detections feasible. For this purpose, we present a new analytical, frequency-domain model for the inspiral-merger-postmerger signal emitted by binary neutron star systems. The inspiral and merger parts of the signals are modeled with IMRPhenomD_NRTidalv2, and we describe the main emission peak of the postmerger with a three-parameter Lorentzian, using two different approaches: one in which the Lorentzian parameters are kept free, and one in which we model them via quasiuniversal relations. We test the performance of our new complete waveform model in parameter estimation analyses, studying simulated signals obtained both from our developed model and by injecting numerical relativity waveforms. We investigate the performance of different detector networks to determine the improvement that future detectors will bring to our analysis. We consider Advanced $\mathrm{LIGO}+$ and Advanced $\mathrm{Virgo}+$, KAGRA, and LIGO-India. We also study the possible impact of a detector with high sensitivity in the kilohertz band like NEMO, and finally we compare these results to the ones we obtain with third-generation detectors, the Einstein Telescope and the Cosmic Explorer.

We compare void size and clustering statistics for nDGP and $f(R)$ gravity models and general relativity (GR) using N-body simulations. We show how it is critical to consider the statistics derived from mock galaxy catalogs rather than the dark matter halos alone. Marked differences between the void size functions for GR and $f(R)$ models which present when voids are identified using dark matter halos are removed when voids are identified, more realistically, from mock galaxy tracers of the halos. The void radial velocities and velocity dispersions in the $f(R)$ and nDGP models are enhanced relative to GR in both halos and mock galaxy identified voids. Despite this, we find that the redshift space void quadrupole moments derived from the mock galaxy tracers are strikingly similar across the three gravity models. The Gaussian streaming model (GSM) is shown to accurately reconstruct ${\xi }_2$ in modified gravity models, and we employ the GSM, using a functional derivative approach, to analyze the insensitivity of ${\xi }_2$ to the gravity model. Assuming linear theory, we show the void quadrupole to be an unbiased estimator of the redshift space growth rate parameter $\beta =f/b$ in the modified gravity theories.

Observations by the current generation of gravitational-wave detectors have been pivotal in expanding our understanding of the universe. Although tens of exciting compact binary mergers have been observed, neutron star-black hole (NSBH) mergers remained elusive until they were first confidently detected in 2020. The number of NSBH detections is expected to increase with sensitivity improvements of the current detectors and the proposed construction of new observatories over the next decade. In this work, we explore the NSBH detection and measurement capabilities of these upgraded detectors and new observatories using the following metrics: network detection efficiency and detection rate as a function of redshift, distributions of the signal-to-noise ratios, the measurement accuracy of intrinsic and extrinsic parameters, the accuracy of sky position measurement, and the number of early-warning alerts that can be sent to facilitate the electromagnetic follow-up. Additionally, we evaluate the prospects of performing multimessenger observations of NSBH systems by reporting the number of expected kilonova detections with the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope. We find that as many as $\mathcal{O}(10)$ kilonovae can be detected by these two telescopes every year, depending on the population of the NSBH systems and the equation of state of neutron stars.

In view of the next LIGO-Virgo-KAGRA Observing period O4 (to start in Spring 2023), we address the question of the ability of the interferometers network to discriminate among different neutron stars equation of states better than what was possible with the observation of the binary neutron stars merger GW170817. We show that the observation of an event similar to GW170817 during O4 would allow us to resolve the dimensionless effective tidal deformability $\tilde{\mathrm{\Lambda }}$ within an uncertainty 7 times better than the one obtained in O2. Thanks to the expected increase in sensitivities, we show that any GW170817-like single-event within a distance of 100 Mpc would imply significantly improved constraints of the neutron stars equations of state. We also illustrate the important impact of the noise in the analysis of the signal, showing how it can impact the effective tidal deformability probability density function for large signal-to-noise ratio.

The $f(R,T)$ gravity is a model whose action contains an arbitrary function of the Ricci scalar $R$ and the trace of the energy-momentum tensor $T$. We consider the minimally coupled model $f(R,T)=\chi (R)+\phi (T)$ and shown that, for perfect fluids, the analysis of dynamical equations are sufficient to determine how $\phi$ depends on $T$, independently of the matter fields equation of state and the geometry of space-time. Imposing the energy-momentum tensor conservation we obtain that the trace dependent part $\phi$ must be linear in $T$, apart from the trivial case of a constant. However, the linear dependence on $T$ is severely constrained using the full Will-Nordtvedt version of the parametrized post-Newtonian (PPN) formalism. The result of the PPN analysis is discussed and in addition it is shown that the diffeomorphism invariance of the matter action imposes strong constraints on conservative versions of $f(R,T)$ gravity.

High resolution cosmic microwave background (CMB) experiments have allowed us to precisely measure the CMB temperature power spectrum down to very small scales (multipole $\ell \sim 3000$). Such measurements at multiple frequencies enable separating the power spectrum of the primary CMB anisotropies with the power spectrum of other signals like CMB lensing, thermal and kinematic Sunyaev-Zel’dovich effects (tSZ and kSZ), and cosmic infrared background (CIB). In this paper, we explore another signal of interest at these frequencies that should be present in the CMB maps: extragalactic CO molecular rotational line emissions, which are the most widely used tracers of molecular gas in the line intensity mapping experiments. Using the SIDES simulations adopted for top hat bandpasses at 150 and 220 GHz, we show that the cross-correlation of the CIB with CO lines has a contribution similar to the CIB-tSZ correlation and the kSZ power, thereby contributing a non-negligible amount to the total power at these scales. This signal, therefore, may significantly impact the recently reported $\ge 3\sigma$ detection of the kSZ power spectrum from the South Pole Telescope collaboration, as the contribution of the CO lines is not considered in such analyses. Our results also provide a new way of measuring the CO power spectrum in cross-correlation with the CIB. Finally, these results show that the CO emissions present in the CMB maps will have to be accounted for in all the CMB auto-power spectrum and cross-correlation studies involving a large-scale structure tracer.

The Standard Model Lagrangian has an approximate scale symmetry in the high-energy limit. This observation can be embedded into the fundamental principle of the ultimate theory of nature as the requirement of the exact quantum scale invariance. In this setup, all low-energy particle phenomenology can be obtained as a result of the spontaneous breaking of scale symmetry leading to the presence of the extra massless scalar field—the dilaton. We explore the scenario, in which this field is also capable of solving the strong $CP$ problem in QCD in a similar way as in QCD axion models. The dilaton, playing the role of the axion, is coupled to the QCD sector and acquires a mass term due to nonperturbative breaking of scale symmetry. We show that the dilaton can form dark matter after the low-scale inflation. As a proof of concept, we construct a model of Higgs-driven inflation consistently realizing the axionlike dilaton dark matter production compatible with the cosmic microwave background (CMB) data.