We present a reconstruction algorithm for cosmological models based on $f(\mathcal{Q})$ gravity. We specifically focus on Bianchi type I and Friedmann-Lemaître-Robertson-Walker spacetimes, obtaining exact solutions that might have application in a variety of scenarios such as spontaneous isotropization of Bianchi type I models, dark energy, and inflation, as well as pre-big bang cosmologies.

Gravitational collapse is still poorly understood in the context of $f(R)$ theories of gravity, since the Oppenheimer-Snyder model is incompatible with their junction conditions. In this work, we will present a systematic approach to the problem. Starting with a thorough analysis of how the Oppenheimer-Snyder construction should be generalized to fit within metric $f(R)$ gravity, we shall subsequently proceed to explore the existence of novel exterior solutions compatible with physically viable interiors. Our formalism has allowed us to show that some paradigmatic vacuum metrics cannot represent spacetime outside a collapsing dust star in metric $f(R)$ gravity. Moreover, using the junction conditions, we have found a novel vacuole solution of a large class of $f(R)$ models, whose exterior spacetime is documented here for the first time in the literature as well. Finally, we also report the previously unnoticed fact that the Oppenheimer-Snyder model of gravitational collapse is incompatible with the junction conditions of the Palatini formulation of $f(R)$ gravity.

Scalar-tensor theories leaving significant modifications of gravity at cosmological scales rely on screening mechanisms to recover general relativity (GR) in high-density regions and pass stringent tests with astrophysical objects. Much focus has been placed on the signatures of such modifications of gravity on the propagation of gravitational waves (GWs) through cosmological distances while typically assuming their emission from fully screened regions with the wave generation strictly abiding by GR. Here, we closely analyze the impact of screening mechanisms on the inspiral GW waveforms from compact sources by employing a scaling method that enables a post-Newtonian (PN) expansion in screened regimes. Particularly, we derive the leading-order corrections to a fully screened emission to first PN order in the near zone, and we also compute the modifications in the unscreened radiation zone to second PN order. For a concrete example, we apply our results to a cubic Galileon model. The resulting GW amplitude from a binary black hole inspiral deviates from its GR counterpart at most by one part in ${10}^2$ for the modifications in the radiation zone and at most one part in ${10}^{11}$ due to next-order corrections to the fully screened near zone. We expect such modifications to be undetectable by the current generation of GW detectors, but the deviation is not so small as to remain undetectable in future experiments.

In this work we explore the possibility of incorporating particle physics motivated scalar fields to the dark matter cosmological model. In this landscape, we consider the classical complex scalar field in a certain region in the parameter space of the model that increases the number of neutrino species $N_{\mathrm{eff}}$ in order to be consistent with the observed abundance of light elements produced at big bang nucleosynthesis. We perform analyses using one and two scalar fields. We examine the difference between these models and the priors considered at the edges of the cosmic ladder, this with the purpose of studying the impact of such models on the Hubble cosmic flow. In the two scalar field models we explore the possibility of combining an axion and a Higgs-like field as well as a Higgs-like field and the classical field, we show that in the first case there is no set of parameters that allows us to be consistent with $N_{\mathrm{eff}}$, while in the second case a strong restriction to the set of parameters is obtained. This last restriction is given in terms of a maximum bound of the fraction of Higgs-like field that can be incorporated together with the classical field. Our results could be relevant in the direct dark matter detection programs.

We present directed searches for continuous gravitational waves from the neutron stars in the Cassiopeia A (Cas A) and Vela Jr. supernova remnants. We carry out the searches in the LIGO detector data from the first six months of the third Advanced LIGO and Virgo observing run using the weave semicoherent method, which sums matched-filter detection-statistic values over many time segments spanning the observation period. No gravitational wave signal is detected in the search band of 20–976 Hz for assumed source ages greater than 300 years for Cas A and greater than 700 years for Vela Jr. Estimates from simulated continuous wave signals indicate we achieve the most sensitive results to date across the explored parameter space volume, probing to strain magnitudes as low as $\sim 6.3\times {10}^{-26}$ for Cas A and $\sim 5.6\times {10}^{-26}$ for Vela Jr. at frequencies near 166 Hz at 95% efficiency.

We propose to “gauge” the group of similarity transformations that acts on a space of non-Hermitian scalar theories. We introduce the “similarity gauge field,” which acts as a gauge connection on the space of non-Hermitian theories characterized by (and equivalent to a Hermitian) real-valued mass spectrum. This extension leads to new effects: if the mass matrix is not the same in distant regions of space, but its eigenvalues coincide pairwise in both regions, the particle masses stay constant in the whole spacetime, making the model indistinguishable from a standard, low-energy, and scalar Hermitian one. However, contrary to the Hermitian case, the high-energy scalar particles become unstable at a particular wavelength determined by the strength of the emergent similarity gauge field. This instability corresponds to momentum-dependent exceptional points, whose locations cannot be identified from an analysis of the eigenvalues of the coordinate-dependent squared-mass matrix in isolation, as one might naively have expected. For a doublet of scalar particles with masses of the order of 1 MeV and a similarity gauge rotation of order unity at distances of 1 meter, the corrections to the masses are about ${10}^{-7}\mathrm{eV}$, which makes no experimentally detectable imprint on the low-energy spectrum. However, the instability occurs at ${10}^{18}\mathrm{eV}$, suggestively in the energy range of detectable ultra-high-energy cosmic rays, thereby making this truly non-Hermitian effect and its generalizations of phenomenological interest for high-energy particle physics.

The Forward Physics Facility (FPF), planned to operate near the ATLAS interaction point at the LHC, offers exciting new terrain to explore neutrino properties at TeV energy scales. It will reach an unprecedented regime for terrestrial neutrino experiments and provide the opportunity to reveal new physics of neutrinos at higher energy scales. We demonstrate that future detectors at the FPF have the potential to discover new mediators that couple predominantly to neutrinos, with masses between 0.3 GeV and 20 GeV and small couplings not yet probed by existing searches. Such a neutrinophilic mediator is well motivated for addressing the origin of several neutrino-portal dark matter candidates, including thermal freeze-out and sterile-neutrino dark matter scenarios. Experimentally, the corresponding signatures include neutrino charged-current scattering events associated with large missing transverse momentum, and excessive apparent tau-neutrino events. We discuss the FPF detector capabilities needed for this search, most importantly the hadronic energy resolution.

Using high statistics datasets generated in ($2+1$)-flavor QCD calculations at finite temperature, we present results for low-order cumulants of net-baryon-number fluctuations at nonzero values of the baryon chemical potential. We calculate Taylor expansions for the pressure (zeroth-order cumulant), the net-baryon-number density (first-order cumulant), and the variance of the distribution on net-baryon-number fluctuations (second-order cumulant). We obtain series expansions from an eighth-order expansion of the pressure and compare these to diagonal Padé approximants. This allows us to estimate the range of values for the baryon chemical potential in which these expansions are reliable. We find ${\mu }_B/T\le 2.5$, 2.0, and 1.5 for the zeroth-, first-, and second-order cumulants, respectively. We, furthermore, construct estimators for the radius of convergence of the Taylor series of the pressure. In the vicinity of the pseudocritical temperature $T_{pc}\simeq 156.5\mathrm{MeV}$, we find ${\mu }_B/T\gtrsim 2.9$ at vanishing strangeness chemical potential and somewhat larger values for strangeness neutral matter. These estimates are temperature dependent and range from ${\mu }_B/T\gtrsim 2.2$ at $T=135\mathrm{MeV}$ to ${\mu }_B/T\gtrsim 3.2$ at $T=165\mathrm{MeV}$. The estimated radius of convergences is the same for any higher-order cumulant.

Inspired by the newly observed $T_{cc}^{+}$ state, we systematically investigate the $S$-wave triple-charm molecular states composed of $D^{*}{D}^{*}D$ and $D^{*}{D}^{*}{D}^{*}$. We employ the one-boson-exchange model to derive the interactions between $D(D^{*})$ and $D^{*}$ and solve the three-body Schrödinger equations with the Gaussian expansion method. The $S\text{−}D$ mixing and coupled channel effects are carefully assessed in our study. Our results show that the $I(J^P)=\frac{1}{2}(0^{-},1^{-},2^{-})D^{*}{D}^{*}D$ and $I(J^P)=\frac{1}{2}(0^{-},1^{-},2^{-},3^{-})D^{*}{D}^{*}{D}^{*}$ systems could form bound states, which can be viewed as three-body hadronic molecules. We present not only the binding energies of the three-body bound states, but also the root-mean-square radii of $D\text{−}{D}^{*}$ and $D^{*}\text{−}{D}^{*}$, which further corroborate the molecular nature of these states. These predictions could be tested in the future at LHC or HL-LHC.

The LHCb collaboration reported a fully charmed tetraquark state X(6900) in the invariant mass spectrum of $J/\psi$ pairs in 2020. This discovery inspires us to further study the fully heavy pentaquark system. In this work, we investigate systematically all possible configurations for ground fully heavy pentaquark system via the variational method in the constituent quark model. According to our calculations, we further analyze the relative lengths between quarks and the contributions to the pentaquark masses from different terms of the Hamiltonian. We think no stable states exist in fully heavy pentaquark system. We hope that our study will be helpful to explore for fully heavy pentaquark states.

We develop a procedure to reproduce the ten-dimensional generalized supergravity equations from T-duality covariant equations that facilitates generalization to U-duality covariant formulations of eleven-dimensional supergravity. The latter leads to a modification of the eleven-dimensional supergravity equations with terms that contain a rank-2 tensor field, which is the eleven-dimensional analog of the nonunimodularity Killing vector $I^m$ in ten dimensions.

An exact duality between an axion with arbitrary potential and an antisymmetric form field has been derived some time ago. Using this duality, the axion solution to a strong $CP$ problem has been formulated as a gauge invariant theory of forms. In this description, the QCD axion is represented by a Kalb-Ramond field that is eaten up by the Chern-Simons 3-form of QCD, thereby making it massive. This ensures the $CP$ invariance of the vacuum. Although viewed as an effective low energy theory, this formulation accomplishes the same goal as an ordinary Peccei-Quinn mechanism, due to its gauge invariance, it is protected against unwanted UV corrections. In a previous work it has been shown that dual formulation is insensitive to UV physics in the sense that the corrections to $CP$-conserving vacuum from arbitrary massive sources are strictly zero. By going carefully through duality transformations and source resolution, we reproduce this curious result and give some further consistency checks. We apply a similar analysis to other approaches to naturalness problems based on form fields and axions, such as a cosmological relaxation of the standard model Higgs boson mass via the attractor mechanism.

We construct numerically the symmetric non-Abelian wormholes which are supported by a phantom field in the Einstein-Yang-Mills-Higgs theory beyond the Bogomol’nyi-Prasad-Sommerfield (BPS) limit where the Higgs self-interaction constant $\lambda$ is nonvanishing. Analogous to the BPS limit, the probe limit is the Yang-Mills-Higgs field in the background of the Ellis wormhole when the gravity is switched off. In the presence of gravity, the wormhole solutions possess the Yang-Mills-Higgs hair where families of hairy wormhole solutions emerge from the Ellis wormhole when the gravitational coupling constant increases. In contrast to the BPS limit, the properties of wormholes change drastically when the gravitational strength approaches a critical value for a fixed $\lambda$. The hairy wormholes possess two types of double-throat configurations. The first type is wormholes that develop the double throat when the gravitational strength almost approaches the critical value for lower $\lambda$, whereas the second type is wormholes that exhibit the double throat for a certain range of gravitational strength for higher $\lambda$. These two types of double-throat configurations can coexist for a certain range of $\lambda$ where it is a transition process in which the first type of double throat disappears gradually and the second type of double throat becomes dominant.

A convincing explanation for the nature of the dark energy and dark matter is still missing. In recent works a RG-improved swiss-cheese cosmology with an evolving cosmological constant dependent on the Schücking radius has been proven to be a promising model to explain the observed cosmic acceleration. In this work we extend this model to consider the combined scaling of the Newton constant $G$ and the cosmological constant $\mathrm{\Lambda }$ according to the IR-fixed point hypothesis. We shall show that our model easily generates the observed recent passage from deceleration to acceleration without need of extra energy scales, exotic fields or fine-tuning. In order to check the generality of the concept, two different scaling relations have been analyzed and we proved that both are in very good agreement with $\mathrm{\Lambda }\mathrm{CDM}$ cosmology while one of them has no fine-tuning problem. We also show that our model satisfies the observational local constraints on $\dot{G}/G$.

The standard cosmological model assumes a homogeneous and isotropic universe as the background spacetime on large scales called the cosmological principle. However, some observations suggest the possibility of an inhomogeneous and anisotropic universe at large scales. In this paper, we investigate a model of the Universe with random inhomogeneities and anisotropies on very large scales, motivated by the supercurvature dark energy model in Nan et al. [Phys. Rev. D 99, 103512 (2019)]. In this model, the authors introduced a scalar field with $\mathcal{O}(1)$ inhomogeneities on a scale sufficiently larger than the current horizon scale (superhorizon scale), and the potential energy of the scalar field explains the accelerating expansion, with slight deviations from the cosmological principle. We aim at clarifying the theoretical prediction on the large-scale structure (LSS) of the matter component in this model. Based on the work on the superhorizon scale fluctuations (superhorizon mode) presented in Y. Nan and K. Yamamoto [Phys. Rev. D 105, 063518 (2022)], we derive the equations that the perturbative components to the LSS obey as a generalization of the cosmological perturbations theory, which is solved to find the influence of the dark energy inhomogeneities on the formation of the LSS. Finally, we show that the model can be consistent with observations by comparing the ${\sigma }_8$ predicted by the numerical solution of the model with the ${\sigma }_8$ indicated by observations such as Planck and the Sloan Digital Sky Survey.

Axionlike particles (ALPs) are very light, neutral, spin zero bosons predicted by superstring theory. ALPs interact primarily with two photons, and in the presence of an external magnetic field, they generate photon-ALP oscillations and the change of the polarization state of photons. While well motivated from a theoretical point of view, hints on ALP existence come from astrophysics. In this paper, we state and demonstrate some theorems about a strict relationship between initial photon polarization and photon-ALP conversion probability, which can be extrapolated by observed astrophysical spectra, so that in the presence of ALPs flux-measuring observatories become also polarimeters.

Cosmic-ray antideuterons could be a key for the discovery of exotic phenomena in our Galaxy, such as dark-matter annihilations or primordial black hole evaporation. Unfortunately the theoretical predictions of the antideuteron flux at Earth are plagued with uncertainties from the mechanism of antideuteron production and propagation in the Galaxy. We present the most up-to-date calculation of the antideuteron fluxes from cosmic-ray collisions with the interstellar medium and from exotic processes. We include for the first time the antideuteron inelastic interaction cross section recently measured by the ALICE collaboration to account for the loss of antideuterons during propagation. In order to bracket the uncertainty in the expected fluxes, we consider several state-of-the-art models of antideuteron production and of cosmic-ray propagation.

The extraordinary neutrino flux produced in extreme astrophysical environments like the early Universe, core-collapse supernovae and neutron star mergers may produce coherent quantum neutrino oscillations on macroscopic length scales. The Hamiltonian describing this evolution can be mapped into quantum spin models with all-to-all couplings arising from neutrino-neutrino forward scattering. To date many studies of these oscillations have been performed in a mean-field limit where the neutrinos time evolve in a product state. In this paper we examine a simple two-beam model evolving from an initial product state and compare the mean-field and many-body evolution. The symmetries in this model allow us to solve the real-time evolution for the quantum many-body system for hundreds or thousands of spins, far beyond what would be possible in a more general case with an exponential number ($2^N$) of quantum states. We compare mean-field and many-body solutions for different initial product states and ratios of one- and two-body couplings, and find that in all cases in the limit of infinite spins the mean-field (product state) and many-body solutions coincide for simple observables. This agreement can be understood as a consequence of the fact that the typical initial condition represents a very local but dense distribution about a mean energy in the spectrum of the Hamiltonian. We explore quantum information measures like entanglement entropy and purity of the many-body solutions, finding intriguing relationships between the quantum information measures and the dynamical behavior of simple physical observables.

We estimate the amount of ${}^{37}\mathrm{Ar}$ produced in natural xenon via cosmic-ray-induced spallation, an inevitable consequence of the transportation and storage of xenon on the Earth’s surface. We then calculate the resulting ${}^{37}\mathrm{Ar}$ concentration in a 10-tonne payload (similar to that of the LUX-ZEPLIN experiment) assuming a representative schedule of xenon purification, storage, and delivery to the underground facility. Using the spallation model by Silberberg and Tsao, the sea-level production rate of ${}^{37}\mathrm{Ar}$ in natural xenon is estimated to be $0.024\mathrm{atoms}/\mathrm{kg}/\mathrm{day}$. Assuming the xenon is successively purified to remove radioactive contaminants in 1-tonne batches at a rate of $1\mathrm{tonne}/\mathrm{month}$, the average ${}^{37}\mathrm{Ar}$ activity after 10 tons are purified and transported underground is $0.058-0.090\mu \mathrm{Bq}/\mathrm{kg}$, depending on the degree of argon removal during above-ground purification. Such cosmogenic ${}^{37}\mathrm{Ar}$ will appear as a noticeable background in the early science data, while decaying with a 35-day half-life. This newly noticed production mechanism of ${}^{37}\mathrm{Ar}$ should be considered when planning for future liquid-xenon-based experiments.

Since the publication of our paper [Phys. Rev. D 93, 114508 (2016)], we have found a series of typographical mistakes in the equations shown. In particular, expressions written for the Lellouch-Lüscher factor and the transition amplitudes were those relevant for a basis of definite $\pi \pi$ isospin, while the numerical results presented were those for a basis of definite pion charge states. In this erratum, we explain and correct the typographical errors, which do not alter the numerical results presented.