We present a method to generate static solutions in the Einstein-Maxwell system with a (phantom) dilaton field in $n(\ge 4)$ dimensions, based upon the symmetry of the target space for the nonlinear sigma model. Unlike the conventional Einstein-Maxwell-dilaton system, there appears a critical value of the coupling constant for a phantom dilaton field. In the noncritical case, the target space is $\mathbb{R}\times \mathrm{SL}(2,\mathbb{R})/H$ with the maximal subgroup $H=\{\mathrm{SO}(2),\mathrm{SO}(1,1)\}$, whereas in the critical case the target space becomes a symmetric pp-wave and the corresponding Killing vectors form a non-semi-simple algebra. In either case, we apply the formalism to charge up the neutral solutions and show the analytical expression for dilatonic charged versions of (i) the Fisher solution, (ii) the Gibbons solution, and (iii) the Ellis-Bronnikov solution. We discuss global structures of these solutions in detail. It turns out that some solutions contained in the Fisher and Gibbons classes possess the parallelly propagated (p.p) curvature singularities in the parameter region where all the scalar curvature invariants remain bounded. These p.p curvature singularities are not veiled by a horizon, thrusting them into physically untenable nakedly singular spacetimes. We also demonstrate that the dilatonic-charged Ellis-Bronnikov solution admits a parameter range under which the solution represents a regular wormhole spacetime in the two-sided asymptotically flat regions.

We discuss various novel features of $n(\ge 4)$-dimensional spacetimes sourced by a massless (non)phantom scalar field in general relativity. Assuming that the metric is a warped product of static two-dimensional Lorentzian spacetime and an ($n-2$)-dimensional Einstein space $K^{n-2}$ with curvature $k=0,\pm 1$, and that the scalar field depends only on the radial variable, we present a complete classification of static solutions for both signs of kinetic term. Contrary to the case with a nonphantom scalar field, the Fisher solution is not unique, and there exist two additional metrics corresponding to the generalizations of the Ellis-Gibbons solution and the Ellis-Bronnikov solution. We explore the maximal extension of these solutions in detail by the analysis of null/spacelike geodesics and singularity. For the phantom Fisher and Ellis-Gibbons solutions, we find that there inevitably appear parallelly propagated (p.p) curvature singularities in the parameter region where there are no scalar curvature singularities. Interestingly, the areal radius blows up at these p.p curvature singularities, which are nevertheless accessible within a finite affine time along the radial null geodesics. It follows that only the Ellis-Bronnikov solution describes a regular wormhole in the two-sided asymptotically flat spacetime. Using the general transformation relating the Einstein and Jordan frames, we also present a complete classification of solutions with the same symmetry coupled to a conformal scalar field. Additionally, by solving the field equations in the Jordan frame, we prove that this classification is genuinely complete.

In this paper, working in a Friedman-Lemaitre-Robertson-Walker (FLRW) space-time, we recover, without invoking unconventional exotic matter, the generalized Friedman equation of quantum loop cosmology, and therefore the cosmological bounce. We obtain this result proposing a new model in the framework of modified teleparallel gravity, where the Ricci scalar is replaced by the torsion scalar $T$. Furthermore we show that the associated perturbations again in a flat FLRW space-time are not affected by superluminarities or gradient instabilities. Then, we generalize the results to the curved FLRW space-time by using an appropriate formulation. In this context, the results of the Born-Infeld model are also investigated.

We examine the relation between the Szekeres models and relativistic Lagrangian perturbation schemes, in particular the relativistic Zel’dovich approximation (RZA). We show that the second class of the Szekeres solutions is exactly contained within the RZA when the latter is restricted to an irrotational dust source with a flow-orthogonal foliation of spacetime. In such a case, the solution is governed by the first principal scalar invariant of the deformation field, proving a direct connection with a class of Newtonian three-dimensional solutions without symmetry. For the second class, a necessary and sufficient condition for the vanishing of cosmological backreaction on a scale of homogeneity is expressed through integral constraints. Domains with no backreaction can be smoothly matched, forming a lattice model, where exact deviations average out at a given scale of homogeneity, and the homogeneous and isotropic background is recovered as an average property of the model. Although the connection with the first class of Szekeres solutions is not straightforward, this class allows for the interpretation in terms of a spatial superposition of nonintersecting fluid lines, where each world line evolves independently and under the RZA model equations, but with different associated “local backgrounds”. This points to the possibility of generalizing the Lagrangian perturbation schemes to structure formation models on evolving backgrounds, including global cosmological backreaction.

Cosmological measurements of the 21-cm line of neutral hydrogen are poised to dramatically enhance our understanding of the early universe. In particular, both the epochs of reionization and cosmic dawn remain largely uncharted, and the 21-cm signal is one of the few probes to reach them. Conceptually, the simplest 21-cm measurement is the global signal (GS), which corresponds to the averaged absorption or emission of 21-cm photons across the entire sky. While bright radio foregrounds swamp the cosmic signal over the entire frequency range observable, presenting a formidable hurdle, they can in principle be subtracted, given enough sensitivity. Here, however, we point out an additional—and irreducible—source of uncertainty for the 21-cm GS: cosmic variance. The cosmic-variance noise arises from the finite volume of the universe accessible to 21-cm experiments. Due to the cosmological redshifting of 21-cm photons, each observed frequency probes our universe during a particular cosmic age, corresponding to a narrow redshift slice. The presence of large 21-cm fluctuations makes the GS within each slice different than the GS averaged over the entire universe. We estimate the size of this cosmic-variance noise, and find that for a standard scenario it has a size of $\sim 0.1\mathrm{mK}$, which is $\sim 10\%$ of the size of the expected instrumental noise of a year-long experiment. Interestingly, cosmic variance can overtake instrumental noise for scenarios with extreme 21-cm fluctuations, such as those suggested to explain the sharpness of the claimed EDGES detection. Moreover, as large-scale 21-cm fluctuations are coherent over long distances, cosmic variance correlates the measurements of the GS at nearby redshifts, leading to off-diagonal uncertainties that have so far been neglected.

The framework of a kind of noncanonical warm inflation is introduced, and the dynamical equations of this scenario are presented. We propose slow-roll approximations and redefine slow-roll parameters that remain dimensionless for this scenario. Performing systemic stability analysis, we calculate the slow-roll conditions that guarantee that the slow-roll approximations hold. The slow-roll conditions suggest that slow-roll inflation in the general noncanonical warm inflationary scenario remains, and the slow-roll approximations are more easily satisfied. We finally investigate a concrete Dirac-Born-Infeld warm inflationary model.

There is no unique way to describe the dark energy–dark matter interaction, as we have little information about the nature and dynamics of the dark sector. Hence, in many of the phenomenological dark matter fluid interaction models in the literature, the interaction strength $Q_{\nu }$ in the dark sector is introduced by hand. Demanding that the interaction strength $Q_{\nu }$ in the dark sector must have a field theory description, we obtain a unique form of the interaction strength. We show the equivalence between the fields and fluids for the $f(R,\chi )$ model where $f$ is an arbitrary, smooth function of $R$ and a classical scalar field $\chi$, which represents dark matter. Up to first order in perturbations, we show that the one-to-one mapping between the classical field theory description and the phenomenological fluid description of interacting dark energy and dark matter exists only for this unique form of interaction. We then classify the interacting dark energy models considered in the literature into two categories based on the field-theoretic description. We introduce a novel autonomous system and its stability analysis for the general interacting dark sector. We show that the dark-energy-dominated epoch occurs earlier than the noninteracting systems for a specific scalar field potential and a range of coupling strengths.

A successful baryogenesis mechanism is proposed in the cosmological framework of Brans-Dicke modified gravity. Primordial black holes with small mass are produced at the end of the Brans-Dicke field domination era. The Hawking radiation reheats a spherical region around every black hole to a high temperature and the electroweak symmetry is restored there. A domain wall is formed separating the region with the symmetric vacuum from the asymmetric region where electroweak baryogenesis takes place. First-order phase transition is not needed. In Brans-Dicke cosmologies, black hole accretion can be strong enough to result in cosmic black hole domination, an extension of the lifetime of black holes and enhanced baryogenesis. The analysis of the whole scenario provides very easily and without fine tuning the observed baryon number asymmetry for either small or big $CP$-violating angles in the finite temperature corrected effective potential of two-Higgs-doublet models. The advantage of our proposed scenario with Brans-Dicke modified gravity is that it naturally provides both black hole domination and efficient baryogenesis for smaller $CP$-violating angles compared to the same mechanism applied in a Friedmann-Robertson-Walker cosmological background.

Neutron stars are expected to have a tight relation between their moment of inertia ($I$), tidal deformability ($\lambda$, which is related to the Love number), and rotational mass quadrupole moment ($Q$) that is nearly independent of the unknown equation of state (EOS) of cold dense matter. These and similar relations are often called “universal”, and they have been used for various applications including analysis of gravitational wave data. We extend these studies using piecewise polytropic representations of dense matter, including for so-called twin stars that have a second branch of stability at high central densities. The second-branch relations are less tight, by a factor of $\sim 3$, than the relations found in the first stable branch. We find that the relations on both branches become tighter when we increase the lower limit to the maximum mass for the EOS under consideration. We also propose new empirical relations between $I$, $\lambda$, $Q$, and the complex frequency $\omega ={\omega }_R+i{\omega }_I$ of the fundamental axial $w$-mode, and find that they are comparably tight to the I-Love-Q correlations.

We discuss a cornucopia of potential astrophysical signatures and constraints on magnetically charged black holes of various masses. As recently highlighted, being potentially viable astrophysical candidates with immense electromagnetic fields, they may be ideal windows to fundamental physics, electroweak symmetry restoration, and nonperturbative quantum field theoretic phenomena. We investigate various potential astrophysical pointers and bounds—including limits on charges, location of stable orbits, and horizons in asymptotically flat and asymptotically de Sitter backgrounds, bounds from galactic magnetic fields and dark matter measurements, characteristic electromagnetic fluxes, and tell-tale gravitational wave emissions during binary inspirals. Stable orbits around these objects hold an imprint of their nature and in the asymptotically de Sitter case, there is also a qualitatively new feature with the emergence of a stable outer orbit. We consider binary inspirals of both magnetic and neutral, and magnetic and magnetic, black hole pairs. The electromagnetic emissions and the gravitational waveform evolution, along with interblack hole separation, display distinct features. Many of the astrophysical signatures may be observationally glaring—for instance, even in regions of parameter space where no electroweak corona forms, owing to magnetic fields that are still many orders of magnitude larger than even magnetars, their consequent electromagnetic emissions will be spectacular during binary inspirals. While adding new results, our discussions also complement works in similar contexts, that have appeared recently in the literature.

Galactic core-collapse supernovae are among the possible sources of gravitational waves. We investigate the ability of gravitational-wave observatories to extract the properties of the collapsing progenitor from the gravitational waves radiated. We use simulations of supernovae that explore a variety of progenitor core rotation rates and nuclear equations of state and examine the ability of current and future observatories to determine these properties using gravitational-wave parameter estimation. We use principal component analysis of the simulation catalog to determine the dominant features of the waveforms and create a map between the measured properties of the waveform and the physical properties of the progenitor star. We use Bayesian parameter inference and the parameter map to calculate posterior probabilities for the physical properties given a gravitational-wave observation. We demonstrate our method on a random sample of the waveform catalog that was excluded from construction of the principal component analysis and estimate the ratio of the progenitor’s core rotational kinetic energy to potential energy ($\beta$) and the post bounce oscillation frequency. For a supernovae at the distance of the galactic center (8.1 kpc) with $\beta =0.02$ our method can estimate $\beta$ with a 90% credible interval of 0.004 for Advanced LIGO, improving to 0.0008 for Cosmic Explorer, the proposed third-generation detector. We demonstrate that if the core is rotating sufficiently rapidly for a signal source within the Milky Way observed by Cosmic Explorer, our method can also extract the post bounce oscillation frequency of the protoneutron star to a precision of within 5 Hz (90% credible interval) allowing us to constrain the nuclear equation of state. For a supernovae at the distance of the Magellanic Clouds (48.5 kpc) Cosmic Explorer’s ability to measure these parameters decreases slightly to 0.003 for rotation and 11 Hz for the postbounce oscillation frequency (90% credible interval). Sources in Magellanic Clouds with $\beta <0.02$ will be too distant for Advanced LIGO to measure these properties.

Dirac materials, because of their small $\mathcal{O}(\mathrm{meV})$ band gap, are a promising target for dark photon-mediated scattering and absorption of light dark matter. In this paper, we characterize the daily modulation rate of dark matter interacting with a Dirac material due to anisotropies in their crystal structure. We show that daily modulation is an $\mathcal{O}(1)$ fraction of the total rate for dark matter scattering in the Dirac material ${\mathrm{ZrTe}}_5$. When present, the modulation is dominated by the orientation of the material’s dielectric tensor with respect to the dark matter wind and is maximized when the crystal is oriented such that the dark matter wind is completely aligned with the largest and smallest components of the dielectric tensor at two different times of the day. Because of the large modulation, any putative dark matter scattering signal could be rapidly verified or ruled out by changing the orientation of the crystal with respect to the wind and observing how the daily modulation pattern changes.

In the framework of a phenomenological model based on an effective Lagrangian, that allows us to exploit all available data, we have obtained the strong, electromagnetic and mixed strong-electromagnetic amplitudes of the $\psi (2S)$ decays into baryon-antibaryon pairs. The analysis, repeating the procedure successfully implemented in the case of the leading vector charmonium $J/\psi$, revealed a new and quite intriguing phenomenon, that by itself triggered a further quite interesting finding. The phenomenon is the high affinity of the $\psi (2S)$ meson with the $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ pair, at a level that cannot be justified by the model. As a consequence, we excluded the $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ channel from the set of experimental constraints by largely improving the description power of the model, which then led to another interesting result: the QCD regime turned out to be perturbative already at the $\psi (2S)$ mass. Finally, the comparison with the results obtained for the $J/\psi$ has shown that the main difference with respect to the $\psi (2S)$ concerns the SU(3) breaking source due to the quark mass difference. As expected, consequently to its larger mass, the effects of such a difference are less important for the $\psi (2S)$ with respect to the $J/\psi$ meson.

The clockwork mechanism, which can naturally explain the origin of small numbers, is implemented in $SO(10)$ grand unified theories to address the origin of hierarchies in fermion masses and mixings. We show that a minimal Yukawa sector involving a $10_H$ and ${\overline{126}}_H$ of Higgs bosons, extended with two clockwork chains consisting of $16+\overline{16}$ vectorlike fermions, can explain the hierarchical patterns with all the Yukawa couplings being of order one. Emergence of a realistic mass spectrum does not require any symmetry that distinguishes the three generations. We develop clockwork-extended $SO(10)$ GUTs both in the context of SUSY and non-SUSY frameworks. Implementation of the mechanism in non-SUSY scenario assumes a Peccei-Quinn symmetry realized at an intermediate scale, with the clockwork sector carrying nontrivial charges, which solves the strong $CP$ problem and provides axion as a dark matter candidate.

We investigate the minimal $U(1{)}_{L_{\mu }-L_{\tau }}$ model with extra heavy vectorlike leptons or charged scalars. By studying the kinetic mixing between $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge boson $Z^{\prime }$ and standard model photon, which is absent at tree level and will arise at one-loop level due to $\mu$, $\tau$, and new heavy charged leptons or scalars, the interesting behavior is shown. It can provide the possibility for visible signatures of new heavy particles. We propose to search for $Z^{\prime }$ at electron collider experiments, such as Belle II, BESIII, and future Super Tau Charm Factory (STCF), using the monophoton final state. The parameter space of $Z^{\prime }$ is probed and scanned by its gauge coupling constant $g_{Z^{\prime }}$ and mass $m_{Z^{\prime }}$. We find that electron colliders have sensitivity to the previously unexplored parameter space for $Z^{\prime }$ with MeV–GeV mass. Future STCF experiments with $\sqrt{s}=2–7\mathrm{GeV}$ can exclude the anomalous muon magnetic moment favored area when $m_{Z^{\prime }}<5\mathrm{GeV}$ with the luminosity of $30{\mathrm{ab}}^{-1}$. For $m_{Z^{\prime }}<2m_{\mu }$, $g_{Z^{\prime }}$ can be down to $4.2\times {10}^{-5}$ at 2 GeV STCF.

We study a mechanism of generation of Majorana neutrino mass due to spontaneous breaking of chiral symmetry (SBCS) accompanied by the formation of a quark condensate. The effect of the condensate is transmitted to the neutrino sector via lepton-number violating (LNV) lepton-quark dimension-7 operators known in the literature as an origin of the neutrino-mass-independent mechanism of neutrinoless double-beta ($0\nu \beta \beta$) decay. The smallness of neutrino masses is due to a large ratio between the LNV scale and the scale of the SBCS. This is a new realization of the seesaw mechanism, which we dub the quark condensate seesaw (QCSS). We examine the predictions of the QCSS for $0\nu \beta \beta$-decay and neutrino mass spectrum. We will show that our model predicts the normal neutrino mass ordering and narrow ranges of the neutrino masses.

A very economic scenario with just three extra scalar fields beyond the Standard Model is invoked to explain the muon anomalous magnetic moment, the requisite relic abundance of dark matter as well as the XENON1T excess through the inelastic down-scattering of the dark scalar.

Quantum computing may offer the opportunity to simulate strongly interacting field theories, such as quantum chromodynamics, with physical time evolution. This would give access to Minkowski-signature correlators, in contrast to the Euclidean calculations routinely performed at present. However, as with present-day calculations, quantum computation strategies still require the restriction to a finite system size, including a finite, usually periodic, spatial volume. In this work, we investigate the consequences of this in the extraction of hadronic and Compton-like scattering amplitudes. Using the framework presented in Briceño et al. [Phys. Rev. D 101, 014509 (2020)], we estimate the volume effects for various $1+1\mathrm{D}$ Minkowski-signature quantities and show that these can be a significant source of systematic uncertainty, even for volumes that are very large by the standards of present-day Euclidean calculations. We then present an improvement strategy, based in the fact that the finite volume has a reduced symmetry. This implies that kinematic points, which yield the same Lorentz invariants, may still be physically distinct in the periodic system. As we demonstrate, both numerically and analytically, averaging over such sets can significantly suppress the unwanted volume distortions and improve the extraction of the physical scattering amplitudes. As the improvement strategy is based only in kinematics, it can be applied without detailed knowledge of the system.

We use nonperturbative lattice calculations to investigate the finite-temperature confinement transition of stealth dark matter, focusing on the regime in which this early-Universe transition is first order and would generate a stochastic background of gravitational waves. Stealth dark matter extends the standard model with a new strongly coupled SU(4) gauge sector with four massive fermions in the fundamental representation, producing a stable spin-0 “dark baryon” as a viable composite dark matter candidate. Future searches for stochastic gravitational waves will provide a new way to discover or constrain stealth dark matter, in addition to previously investigated direct-detection and collider experiments. As a first step to enabling this phenomenology, we determine how heavy the dark fermions need to be in order to produce a first-order stealth dark matter confinement transition.

We make predictions for the production and decays of $X(2900)$ states, and their possible charged partners, in $B^{+}$ and $B^0$ decays, considering a number of competing models for the states, including triangle diagrams mediated by quark exchange or pion exchange, and resonance scenarios including molecules and tetraquarks. Assuming only isospin symmetry and the dominance of color-favored weak decays, we find characteristic differences in the predictions of the different models. Future experimental studies can therefore discriminate among the competing interpretations for the states.