Neutron star (NS) equation of state (EoS) insensitive relations or universal relations (UR) involving neutron star bulk properties play a crucial role in gravitational-wave astronomy. Considering a wide range of equations of state originating from (i) phenomenological relativistic mean field models, (ii) realistic EoS models based on different physical motivations, and (iii) polytropic EoSs described by spectral decomposition method, we update the EoS-insensitive relations involving NS tidal deformability (multipole Love relation) and the UR between $f$-mode frequency and tidal deformability ($f$-Love relation). We analyze the binary neutron star event GW170817 using the frequency domain TaylorF2 waveform model with updated universal relations and find that the additional contribution of the octupolar electric tidal parameter and quadrupolar magnetic tidal parameter or the change of multipole Love relation has no significant impact on the inferred NS properties. However, adding the $f$-mode dynamical phase lowers the 90% upper bound on $\tilde{\mathrm{\Lambda }}$ by 16–20% as well as lowers the upper bound of NSs radii by $\sim 500\mathrm{m}$. The combined URs (multipole Love and $f$-Love) developed in this work predict a higher median (also a higher 90% upper bound) for $\tilde{\mathrm{\Lambda }}$ by 6% and also predict higher radii for the binary components of GW170817 by 200–300 m compared to the URs used previously in the literature. We further perform injection and recovery studies on simulated events with different EoSs in $\mathrm{A}+$ detector configuration as well as with the third generation Einstein Telescope. In agreement with the literature, we find that neglecting $f$-mode dynamical tides can significantly bias the inferred NS properties, especially for low mass NSs. However, we also find that the impact of the URs is within statistical errors.

The production of radioactive isotopes by interactions of cosmic-ray particles with sodium iodide (NaI) crystals can produce radioactive backgrounds in detectors used to search for rare events. Through controlled irradiation of NaI crystals with a neutron beam that matches the cosmic-ray neutron spectrum, followed by direct counting and fitting the resulting spectrum across a broad range of energies, we determined the integrated production rate of several long-lived radioisotopes. The measurements were then extrapolated to determine the sea-level cosmogenic neutron activation rate, including the first experimental determination of the tritium production rate: $(80\pm 21)\mathrm{atoms}/\mathrm{kg}/\mathrm{day}$. These results will help constrain background estimates and determine the maximum time that NaI-based detectors can remain unshielded above ground before cosmogenic backgrounds impact the sensitivity of next-generation experiments.

We show how the conic hull method, recently developed for the analytic and noniterative evaluation of multifold Mellin-Barnes (MB) integrals, can be extended to the case where these integrals have straight contours of integration parallel to the imaginary axes in the complex planes of the integration variables. MB integrals of this class appear, for instance, when one computes the $\epsilon$-expansion of dimensionally regularized Feynman integrals, as a result of the application of one of the two main strategies (called A and B in the literature) used to resolve the singularities in $\epsilon$ of MB representations. We upgrade the Mathematica package MBConicHulls.wl which can now be used to obtain multivariable series representations of multifold MB integrals with arbitrary straight contours, providing an efficient tool for the automatic computation of such integrals. This new feature of the package is presented, along with an example of application by calculating the $\epsilon$-expansion of the dimensionally regularized massless one-loop pentagon integral in general kinematics and $D=4-2\epsilon$.

We propose a scenario where dark matter (DM) can be generated nonthermally due to the presence of a light Dirac neutrino portal between the standard model (SM) and dark sector particles. The SM is minimally extended by three right-handed neutrinos (${\nu }_R$), a Dirac fermion DM candidate ($\psi$) and a complex scalar ($\varphi$), transforming nontrivially under an unbroken ${\mathbb{Z}}_4$ symmetry while being singlets under the SM gauge group. While DM and ${\nu }_R$ couplings are considered to be tiny in order to be in the nonthermal or freeze-in regime, $\varphi$ can be produced either thermally or nonthermally depending upon the strength of its Higgs portal coupling. We consider both these possibilities and find out the resulting DM abundance via freeze-in mechanism to constrain the model parameters in the light of Planck 2018 data. Since the interactions producing DM also produce relativistic ${\nu }_R$, we check the enhanced contribution to the effective relativistic degrees of freedom $\mathrm{\Delta }{\mathrm{N}}_{\mathrm{eff}}$ in view of existing bounds as well as future sensitivities. We also check the stringent constraints on free-streaming length of such freeze-in DM from structure formation requirements. Such constraints can rule out DM mass all the way up to $\mathcal{O}(100\mathrm{keV})$ keeping the $\mathrm{\Delta }{\mathrm{N}}_{\mathrm{eff}}\le \mathcal{O}({10}^{-3})$ out of reach from near future experiments. Possible extensions of this minimal model can lead to observable $\mathrm{\Delta }{\mathrm{N}}_{\mathrm{eff}}$ which can be probed at next generation experiments.

Future $c\text{−}\tau$ factories are natural places to study extensions of the Standard Model (SM) of particle physics with new long-lived feebly interacting particles light enough to be produced in electron-positron collisions. We investigate prospects of these machines in exploring such extensions emphasizing the role of polarized beams in getting rid of the SM irreducible background for the missing energy signature. We illustrate this on the example of the $c\text{−}\tau$ project in Novosibirsk, where the electron beam is designed to be polarized to achieve much higher sensitivity to hadronic resonances and $\tau$ leptons. We investigate models with hidden photons, with millicharged particles (fermions and scalars), with $Z^{\prime }$ bosons and with axionlike particles. We find that the electron beam polarization of 80% significantly improves the chances to observe the signal, especially with large statistics. We outline the regions of the model parameter space which can be reached at this factory in one year and in ten years of operation according with the scientific schedule of tuning the energy of colliding beams.

The little Randall-Sundrum (little RS) model receives significantly stronger constraints from the flavor observables in comparison to the Randall-Sundrum (RS) model. In this paper, we analyze the effect of the electroweak sector in little RS on flavor-changing decays of charged leptons. We compare the predictions of the model with the current limits on the flavor-violating branching ratios of $\mu \to eee$, $\tau \to eee$, $\tau \to \mu \mu \mu$, $\tau \to \mu ee$, $\tau \to e\mu \mu$, $\mu \to e\gamma$, and $\mu Ti\to eTi$, and we show that the dominant constraint arises from the $\mu Ti\to eTi$ process which strongly limits the KK-1 gauge boson mass ($M_{KK}$) to be $\gtrsim 30.7\mathrm{TeV}$. We then derive and show that generalizing the electroweak gauge sector to include the brane localized kinetic term relaxes this constraint to $\gtrsim 12\mathrm{TeV}$. Toward the conclusion, we comment on the possibility that the large flavor-violating currents can be mitigated by relaxing the assumption regarding the unnatural thinness and rigidity of the UV brane and discuss the possibility of suppression of these currents in the presence of fat fluctuating branes.

The total and differential cross sections of elastic proton-proton and proton-antiproton scattering are studied in a holographic QCD model, considering the Pomeron and Reggeon exchanges in the Regge regime. In our model setup, the Pomeron and Reggeon exchanges are described by the Reggeized spin-2 glueball and vector meson propagators, respectively. How those contributions change with the energy is explicitly shown, focusing on the contribution ratios. The adjustable parameters included in the model are determined with the experimental data, and it is presented that the resulting total and differential cross sections are consistent with the data in a wide kinematic region.

In this work, we construct the Lagrangian describing meson-diquark interaction, such that the diquark-anti-diquark component as well as the molecular component is introduced when studying the $Z_{cs}$ states. In this way, the problem is solved that if only considering the ${\overline{D}}^{(*)}{D}_s^{(*)}$ components, the potentials are suppressed by the OZI rule. Through solving the Bethe-Salpeter equation, we find that the $Z_{cs}(4000{)}^{+}$ can be explained as the mixture of ${\overline{D}}^{*0}{D}_s^{+}$ and ${\overline{A}}_{cs}{S}_{cu}$ components. Besides, for the ${\overline{D}}^{*0}{D}_s^{*+}/{\overline{A}}_{cs}{A}_{cu}$ system, the pole of $4208\pm 13i\mathrm{MeV}$ on the second Riemann sheet is predicted, whose mass agrees with that of $Z_{cs}(4220{)}^{+}$ while the width is much smaller than $Z_{cs}(4220{)}^{+}$. Due to the large error of the $Z_{cs}(4220{)}^{+}$’s width, further measurements are expected. In addition, several other poles of different spins are predicted.

We compute the electromagnetic charged kaon form factor in the timelike region by employing a Poincaré covariant formalism of the Bethe-Salpeter equation to study quark-antiquark bound states in conjunction with the Schwinger-Dyson equation for the quark propagator. Following a recent kindred calculation of the timelike electromagnetic pion form factor, we include the most relevant intermediate composite particles permitted by their quantum numbers in the interaction kernel to allow for a decay mechanism for the resonances involved. This term augments the usual gluon mediated interaction between quarks. For a sufficiently low energy timelike probing photon, the electromagnetic form factor is saturated by the $\rho (770)$ and $\varphi (1020)$ resonances. We assume $SU(2)$ isospin symmetry throughout. Our results for the absolute value squared of the electromagnetic form factor agree qualitatively rather well and quantitatively moderately so with available experimental data.

We report the first calculation using physical light-quark masses of the electromagnetic form factor $V(z)$ describing the long-distance contributions to the $K^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$ decay amplitude. The calculation is performed on a $2+1$ flavor domain wall fermion ensemble with inverse lattice spacing $a^{-1}=1.730(4)\mathrm{GeV}$. We implement a Glashow-Iliopoulos-Maiani cancellation by extrapolating to the physical charm-quark mass from three below-charm masses. We obtain $V(z=0.013(2))=-0.87(4.44)$, achieving a bound for the value. The large statistical error arises from stochastically estimated quark loops.

We study the renormalization of the non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric scalar field theory with the interaction ${\varphi }^2(i\varphi {)}^{ϵ}$ using the Wilsonian approach and without any expansion in $ϵ$. Specifically, we solve the Wetterich equation in the local potential approximation, both in the ultraviolet regime and with the loop expansion. We calculate the scale-dependent effective potential and its infrared limit. The theory is found to be renormalizable at the one-loop level only for integer values of $ϵ$, a result which is not yet established within the $ϵ$-expansion. Particular attention is therefore paid to the two interesting cases $ϵ=1,2$, and the one-loop beta functions for the coupling associated with the interaction $i{\varphi }^3$ and $-{\varphi }^4$ are computed. It is found that the $-{\varphi }^4$ theory has asymptotic freedom in four-dimensional spacetime. Some general properties for the Euclidean partition function and $n$-point functions are also derived.

The parametrized post-Einsteinian framework modifies inspiral waveform models to incorporate effects beyond general relativity (GR). We extend the existing model into the merger-ringdown regime. The modification introduced here adds a single degree of freedom that corresponds to a change in the binary coalescence time. Other merger properties remain as predicted by GR. We discuss parameter estimation with this model, and how it can be used to extract information from beyond-GR waveforms.

We study the nonlinear dynamics of binary black hole systems with scalar charge by numerically evolving the full equations of motion for shift-symmetric Einstein scalar Gauss-Bonnet gravity. We consider quasicircular binaries with different mass-ratios, varying the Gauss-Bonnet coupling and quantifying its impact on the emitted scalar and gravitational waves. We compare our numerical results to post-Newtonian calculations of the radiation emitted during the inspiral. We demonstrate the accuracy of the leading-order terms in post-Newtonian theory in modeling the amplitude of the scalar waveform, but find that, at least for the last few orbits before merger, the currently available post-Newtonian theory is not sufficient to model the dephasing of the gravitational wave signal in this theory. We further find that there is non-negligible nonlinear enhancement in the scalar field at merger, but that the effect on the peak gravitational wave emission is small.

I discuss how one can apply the covariant formalism developed by Vilkovisky and DeWitt to obtain frame invariant fifth force calculations for scalar-tensor theories. Fifth forces are severely constrained by astrophysical measurements. It was shown previously that for scale-invariant Higgs-dilaton gravity, in a particular choice of frame, the dilaton fifth force is dramatically suppressed, evading the observational constraints. Using a geometric approach I extend this result to all frames, and show that the usual dichotomy of “Jordan frame” versus “Einstein frame” is better understood as a continuum of frames: submanifold slices of a more general field space.

We use here a family of scaling transformations, that scale key rates in the evolution equations, to analytically understand constraints on light relics from cosmic microwave background (CMB) maps, given cosmological models of varying degrees of complexity. We describe the causes of physical effects that are fundamentally important to the constraining power of the data, with a focus on the two that are most novel. We use as a reference model a cosmological model that admits a scaling transformation that increases light relic energy density while avoiding all of these causes. Constraints on light relics in a given model can then be understood as due to the differences between the given model and the reference model, as long as the additional light relics only interact gravitationally with the Standard Model components. This understanding supports the development of cosmological models that can evade light relics constraints from CMB maps.

Dynamical friction (DF) is the gravitational force experienced by a body moving in a medium as a result of its density wake. In this work, we investigate the DF acting on circularly moving perturbers in fuzzy dark matter (FDM) backgrounds. After condensation in the early Universe, FDM is described by a single wave function satisfying a Schrödinger-Poisson equation. An equivalent, hydrodynamic formulation can be obtained through the Madelung transform. Here, we consider both descriptions and restrict our analysis to linear response theory. We take advantage of the hydrodynamic formulation to derive a fully analytic solution to the DF in steady state and for a finite time perturbation (corresponding to a perturber turned on at $t=0$). We compare our prediction to a numerical implementation of the wave approach that includes a nonvanishing FDM velocity dispersion $\sigma$. Our solution is valid for both a single and a binary perturber in circular motion as long as $\sigma$ does not significantly exceed the orbital speed $v_{\mathrm{circ}}$. While the short-distance Coulomb divergence of the (supersonic) gaseous DF is no longer present, DF in the FDM case exhibits an infrared divergence which stems from the (also) diffusive nature of the Schrödinger equation. Our analysis of the finite time perturbation case reveals that the density wake produced by perturbers diffuses through the FDM medium until it reaches its outer boundary. Once this transient diffusive regime is over, both the radial and tangential DF oscillate about the steady-state solution with a decaying envelope. Steady state is never achieved. We discuss two astrophysical applications of our results: we revisit the DF decay timescales of the five Fornax globular clusters and point out that the inspiral of compact binary may stall because the DF torque about the binary center of mass sometimes flips sign to become a thrust rather than a drag.

We present two complementary NuSTAR x-ray searches for keV-scale dark matter decaying to monoenergetic photons in the Milky Way halo. In the first, we utilize the known intensity pattern of unfocused stray light across the detector planes—the dominant source of photons from diffuse sources—to separate astrophysical emission from internal instrument backgrounds using $\sim 7$- Ms/detector deep blank-sky exposures. In the second, we present an updated parametric model of the full NuSTAR instrument background, allowing us to leverage the statistical power of an independent $\sim 20$-Ms/detector stacked exposures spread across the sky. Finding no evidence of anomalous x-ray lines using either method, we set limits on the active-sterile mixing angle ${\sin }^2(2\theta )$ for sterile-neutrino masses 6–40 keV. The first key result is that we strongly disfavor a $\sim 7$-keV sterile neutrino decaying into a 3.5-keV photon. The second is that we derive leading limits on sterile neutrinos with masses $\sim 15–18\mathrm{keV}$ and $\sim 25–40\mathrm{keV}$, reaching or extending below the big bang nucleosynthesis limit. In combination with previous results, the parameter space for the neutrino minimal standard model is now nearly closed.

Dilatons [$\varphi (x)$] are a class of bosonic scalar particles associated with scaling symmetry and its compensation (under the violations of the same). They are capable of interacting gravitationally with other massive bodies. As they have coupling to two photons ($\gamma$), they are (also) capable of decaying to the two photons. However, the decay time is long and that makes them a good candidate for dark matter. Furthermore due to two photon coupling, they can produce optical signatures in a magnetic field. In a vacuum or plain matter they couple to one of the transversely polarized states of the photon. But in magnetized matter, they couple to both the transversely polarized state of photons (due to the emergence of a parity violating part of the photon self-energy contribution from magnetized matter). Being spin zero scalar, they could mix with spin zero longitudinal part of photons but they do not. A part of this work is directed towards understanding this issue of mixing the scalar with various polarization states of photons in a medium (magnetized or unmagnetized) due to the constraints from different discrete symmetries, e.g., charge conjugation ($\mathbf{C}$), parity ($\mathbf{P}$) and time reversal ($\mathbf{T}$) associated with the interaction. Based on these symmetry aided arguments, the structure of the mixing matrix is found to be $3\times 3$, as in the case of neutrino flavor mixing matrix. Thus there exists nonzero finite probabilities of oscillation between different polarization states of photon to dilaton. Our analytical and numerical analysis show no existence of periodic oscillation length either in temporal or spatial direction for the most general values of the parameters in the theory. Possible astrophysical consequences of these results can be detected through the discussed observations.

It is well known that the neutrino flavor in extreme astrophysical environments changes under the effect of three contributions: the vacuum oscillation, the interaction with the surrounding matter, and the collective oscillations due to interactions between different neutrinos. The latter adds a nonlinear contribution to the equations of motion, making the description of their dynamics complex. In this work we study various strategies to simulate the coherent collective oscillations of a system of $N$ neutrinos in the two-flavor approximation using quantum computation. This was achieved by using a pair-neutrino decomposition designed to account for the fact that the flavor Hamiltonian, in the presence of the neutrino-neutrino term, presents an all-to-all interaction that makes the implementation of the evolution dependent on the qubit topology. We analyze the Trotter error caused by the decomposition demonstrating that the complexity of the implementation of time evolution scales polynomially with the number of neutrinos and that the noise from near-term quantum device simulation can be reduced by optimizing the quantum circuit decomposition and exploiting a full-qubit connectivity. We find that the gate complexity using second order Trotter-Suzuki formulas scales better with system size than with other decomposition methods such as quantum signal processing. We finally present the application and the results of our algorithm on a real quantum device based on trapped-ion qubits.

Bosons carrying a conserved charge can form stable bound states if their Lagrangian contains attractive self-interactions. Bound-state configurations with a large charge $Q$ can be described classically and are denoted as $Q$-balls, their properties encoded in a nonlinear differential equation. Here, we study $Q$-balls in arbitrary polynomial single-scalar-field potentials both numerically and via various analytical approximations. We highlight some surprising universal features of $Q$-balls that barely depend on the details of the potential. The polynomial potentials studied here can be realized in renormalizable models involving additional heavy or light scalars, as we illustrate with several examples.