Infrared (IR) dimension function $d_{\mathrm{IR}}(\lambda )$ characterizes the space effectively utilized by QCD quarks at Dirac scale $\lambda$, and indirectly the space occupied by glue fields. It was proposed that its nonanalytic behavior in thermal infrared phase reflects the separation of QCD system into an IR component and an independent bulk. Here we study the “plateau modes” in the IR component, whose dimensional properties were puzzling. Indeed, in the recent metal-to-critical scenario of transition to IR phase, this low-dimensional plateau connects the Anderson-like mobility edge ${\lambda }_{\mathrm{IR}}=0$ in Dirac spectrum with mobility edges $\pm {\lambda }_{\mathrm{A}}$. For this structure to be truly Anderson-like, plateau modes have to be exponentially localized, implying that both the effective distances $L_{\mathrm{eff}}\propto L^{\gamma }$ and the effective volumes $V_{\mathrm{eff}}\propto L^{d_{\mathrm{IR}}}$ in these modes grow slower than any positive power of IR cutoff $L$. Although $\gamma =0$ was confirmed in the plateau, it was found that $d_{\mathrm{IR}}\approx 1$. Here we apply the recently proposed multidimension technique to the problem. We conclude that a plateau mode of pure-glue QCD at UV cutoff $a=0.085\mathrm{fm}$ occupies a subvolume of IR dimension zero with probability at least 0.9999, substantiating this aspect of metal-to-critical scenario to a respective degree.

We discuss possible future studies of photon-photon (light-by-light) scattering using a planned FoCal and ALICE 3 detectors. We include different mechanisms of $\gamma \gamma \to \gamma \gamma$ scattering such as double-hadronic photon fluctuations, $t/u$-channel neutral pion exchange or resonance excitations ($\gamma \gamma \to R$) and deexcitation ($R\to \gamma \gamma$). The broad range of (pseudo)rapidities and lower cuts on transverse momenta open a necessity to consider not only dominant box contributions but also other subleading contributions. Here we include low mass resonant $R={\pi }^0$, $\eta$, ${\eta }^{\prime }$ contributions. The resonance contributions give intermediate photon transverse momenta. However, these contributions can be eliminated by imposing windows on diphoton invariant mass. We study and quantify individual box contributions (leptonic, quarkish). The electron/positron boxes dominate at low $M_{\gamma \gamma }<1\mathrm{GeV}$ diphoton invariant masses. The $\mathrm{Pb}\mathrm{Pb}\to \mathrm{PbPb}\gamma \gamma$ cross section is calculated within equivalent photon approximation in the impact parameter space. Several differential distributions are presented and discussed. We consider four different kinematic regions. We predict a cross section in the (mb-b) range for typical ALICE 3 cuts, a few orders of magnitude larger than for the current ATLAS or CMS experiments. We also consider the two-${\pi }^0$ background which can, in principle, be eliminated at the new kinematical range for the ALICE 3 measurements by imposing dedicated cuts on diphoton transverse momentum and/or so-called vector asymmetry.

Prompted by the recent discoveries of $T_{c\overline{s}0}(2900{)}^{++}$ in the $D_s^{+}{\pi }^{+}$ invariant mass distribution of $B^{+}\to D^{-}{D}_s^{+}{\pi }^{+}$ process, we present a model that hopes to help us investigate the nature of $T_{c\overline{s}0}(2900{)}^{++}$ by reproducing the mass distribution of $D^{-}{\pi }^{+}$, $D_s^{+}{\pi }^{+}$, and $D^{-}{D}_s^{+}$ in $B^{+}\to D^{-}{D}_s^{+}{\pi }^{+}$ decays. The structure of the triangular singularity peak generated from the ${\chi }_{c1}{D}^{*+}{K}^{*+}$ loop near the $D^{*+}{K}^{*+}$ threshold is considered in our model may be the experimentally discovered resonancelike state structure $T_{c\overline{s}0}(2900{)}^{++}$. In addition, we employ a coupled-channel approach to describe the dominant contribution of the $D\pi$ $S$-wave amplitude, and also consider other excitations. Our model provides a well fit to the invariant mass distributions of $D^{-}{\pi }^{+}$, $D_s^{+}{\pi }^{+}$, and $D^{-}{D}_s^{+}$ simultaneously.

Dark matter sterile neutrinos radiatively decay in the Milky Way, which can be tested with searches for almost monochromatic photons in the x-ray cosmic spectrum. We analyse the data of SRG/ART-XC telescope operated for two years in the all-sky survey mode. With no significant hints in the Galactic diffuse x-ray spectrum we explore models with sterile neutrino masses in 12–40 keV range and exclude corresponding regions of sterile-active neutrino mixing.

With the Large Hadron Collider (LHC) running, we should probe electroweak baryogenesis (EWBG) while probing $CP$ violation ($CPV$) with electron electric dipole moment (eEDM). Rooted in the flavor structure of the Standard Model (SM), the general two Higgs doublet model (g2HDM) with a second set of Yukawa couplings can deliver EWBG while surviving eEDM. We point out a chiral-enhanced top-bottom interference effect that makes $b\to s\gamma$ decay an exquisite window on EWBG and eEDM, and illustrate the importance of the $\mathrm{\Delta }{A}_{CP}$ observable at Belle II.

In this paper we study black hole and black string solutions in five dimensional $N=2$ supergravity theories arising from the compactification of M-theory on Calabi-Yau manifolds. In particular, we consider explicit examples of three parameter Calabi-Yau manifolds which are obtained as hypersurfaces in toric varieties. Using the attractor mechanism, we obtain Bogomol’nyi-Prasad-Sommerfield (BPS) as well as non-BPS black holes in these compactified supergravity theories. We also consider the black string solutions in these models. We analyze the stability of these extremal black brane configurations by computing the recombination factor. We find multiple stable non-BPS attractor solutions in some of these models.

One of the important extensions of Riemann geometry is Weyl geometry, which is essentially based on the ideas of conformal invariance and nonmetricity. A similar non-Riemannian geometry was proposed by Erwin Schrödinger in the late 1940s, in a geometry which is simpler, and (probably) more elegant than the Weyl geometry. Even if it contains nonmetricity, the Schrödinger connection preserves the length of vectors under parallel transport, and thus seems to be more physical than the Weyl connection. Interestingly enough, Schrödinger’s approach did not attract much interest in the field of gravitational physics. It is the goal of the present paper to reconsider the Schrödinger geometry as a potential candidate for a gravitational theory extending standard general relativity. We consider a gravitational action constructed from a length preserving nonmetricity, in the absence of torsion, and investigate its variation in both Palatini and metric formalisms. While the Palatini variation leads to standard general relativity, the metric version of the theory adds some nonmetricity dependent extra terms in the gravitational Einstein equations, which can be interpreted as representing a geometric type dark energy. After obtaining the generalized Friedmann equations, we analyze in detail the cosmological implications of the theory, by considering two distinct models, corresponding to a dark energy satisfying a linear equation of state, and to conserved matter energy, respectively. In both cases we compare the predictions of the Weyl-Schrödinger cosmology with a set of observational data for the Hubble function, and with the results of the $\mathrm{\Lambda }\mathrm{CDM}$ standard paradigm. Our results show that the Weyl-Schrödinger cosmological models give a good description of the observational data, and, for certain values of the model parameters, they can reproduce almost exactly the predictions of the $\mathrm{\Lambda }\mathrm{CDM}$ model. Hence, the Weyl-Schrödinger theory represents a simple, and viable alternative to standard general relativity, in which dark energy is of purely geometric origin.

Traversable wormholes and regular black holes usually represent completely different scenarios. But in the black bounce spacetime they can be described by a same line element, which is very attractive. Furthermore, the black hole photos taken by EHT show that black holes have spin, so spin is an indispensable intrinsic property of black holes in the actual Universe. In this work, we derive a rotating black hole mimicker surrounded by the string cloud (SC), which can be interpolated to represent regular black hole spacetime and traversable wormhole spacetime. We investigate the effect of the spin $a$ and SC parameter $L$ on the observables (shadow radius $R_s$ and distortion ${\delta }_s$) and energy emission rate of the black hole mimicker surrounded by the SC. We find that shadow for this spacetime is very sensitive to the $L$, i.e., the SC parameter can significantly increase the boundary of the shadow.

Static black holes in the conformal anomaly-sourced semiclassical general relativity in four dimensions were recently extended to rotating, stationary solutions. These quantum-corrected black holes show different features compared to the Kerr black hole and need for further extensions. Here we remove the condition of stationarity and find radiating (Kerr-Vaidya-type) solutions in the same theory augmented with a cosmological constant. As long as the coupling constant $\alpha$ of the $A$-type trace anomaly is nonzero, we show that (i) the cosmological constant is bounded from above, i.e., $\mathrm{\Lambda }\le \frac{3}{4\alpha }$; (ii) static black holes exist but they may not be unique; (iii) static black holes do not satisfy the second law of black hole thermodynamics; (iv) static black holes may have unstable inner horizons; (v) in the nonstationary and axially symmetric case, stability of the event horizon and the second law of thermodynamics black holes are problematic.

Understanding the emergence of classical behavior from a quantum theory is vital to establishing the quantum origin for the temperature fluctuations observed in the cosmic microwave background. We show that a real-space approach can comprehensively address the quantum-to-classical transition problem in the leading order of curvature perturbations. To this end, we test spatial bipartitions of quadratic systems for the interplay between three different signatures of classical behavior: (i) decoherence; (ii) peaking of the Wigner function about classical trajectories; and (iii) relative suppression of noncommutativity in observables. We extract these signatures from the covariance matrix of a multimode Gaussian state and address them primarily in terms of entanglement entropy and log-classicality. Through a phase-space stability analysis of spatial subregions via their reduced Wigner function, we ascertain that the underlying cause for the dominance of classicality signatures is the occurrence of gapped inverted mode instabilities. While the choice of conjugate variables enhances some of these signatures, decoherence studied via entanglement entropy is the stronger and more reliable condition for classicality to emerge. We demonstrate the absence of decoherence, which preempts a quantum-to-classical transition of scalar fluctuations in an expanding background in ($1+1$) dimensions using two examples: (i) a Tanh-like expansion; and (ii) a de Sitter expansion. We provide connection between log classicality and particle number by studying the evolution of each normal mode at late times. We then extend the analysis to leading order fluctuations in ($3+1$) dimensions to show that a quantum-to-classical transition occurs in the de Sitter expansion and discuss the relevance of our analysis in distinguishing cosmological models.

We investigate false vacuum decay of a relativistic scalar field initialized in the metastable minimum of an asymmetric double-well potential. The transition to the true ground state is a well-defined initial-value problem in real time, which can be formulated in nonequilibrium quantum field theory on a closed time path. We employ the nonperturbative framework of the two-particle irreducible (2PI) quantum effective action at next-to-leading order in a large-$N$ expansion. We also compare to classical-statistical field theory simulations on a lattice in the high-temperature regime. By this, we demonstrate that the real-time decay rates are comparable to those obtained from the conventional Euclidean (bounce) approach. In general, we find that the decay rates are time dependent. For a more comprehensive description of the dynamics, we extract a time-dependent effective potential, which becomes convex during the nonequilibrium transition process. By solving the quantum evolution equations for the one- and two-point correlation functions for vacuum initial conditions, we demonstrate that quantum corrections can lead to transitions that are not captured by classical-statistical approximations.

Slow roll of the inflaton field defines the standard dynamics of the inflationary epoch. However, the inflationary system deviates from slow roll when it encounters an extremely flat region of the inflaton potential, and enters a phase dubbed ultraslow roll. In this article, we explore the possibility of realizing an ultraslow-roll phase in a particularly interesting inflationary scenario, called warm inflation. In the warm inflationary scenario a thermalized, subdominant radiation bath coexists with the inflaton energy density as an effect of dissipative dynamics. We show in this article that though the background dynamics indicate ultraslow roll when the potential becomes extremely flat, in warm inflation models, where the dissipation coefficient is a sole function of the temperature of the radiation bath, the system fails to maintain the thermal equilibrium as soon as it enters the ultraslow-roll phase. As thermal equilibrium is a key feature of warm inflation, and as it is not yet known how to deal with warm inflation without thermal equilibrium, we could not analyze such systems any further in this article. However, we demonstrate that brief periods of the ultraslow-roll phase, which smoothly ends in a standard slow roll, can be accommodated in warm inflation (WI) models where the dissipation coefficient is not only a function of the temperature of the radiation bath but also depends on the amplitude of the inflaton field. We theoretically determine the criteria of successfully embedding ultraslow roll in WI while the system remains in thermal equilibrium, and also demonstrate numerically that such short ultraslow-roll phases can indeed be embedded in specific warm inflation models which comply with the theoretically determined criteria.

There may exist extended configurations in the dark matter sector that are analogs of structures in the visible sector. In this work, we explore nontopological solitonic configurations, specifically $Q$-balls, and study when they may form macroscopic astrophysical structures and what their distinct characteristics might be. We study in some detail theoretical bounds on their sizes and constraints on the underlying parameters, based on criteria for an astrophysical $Q$-ball’s existence, gravitational stability and viability of solutions. Following this path, one is able to obtain novel limits on astrophysical $Q$-ball sizes and their underlying parameters. We also explore the gravitational lensing features of different astrophysical $Q$-ball profiles, which are more general than the simple thin-wall limit. It is seen that the magnification characteristics may be very distinct, depending on the actual details of the solution, even for astrophysical $Q$-balls having the same size and mass. Assuming that such astrophysical $Q$-balls may form a small component of the dark matter in the Universe, we place limits on this fraction from the gravitational microlensing surveys EROS-2, OGLE-IV, HSC-Subaru and the proposed future survey WFIRST. Exploring various astrophysical $Q$-ball profiles and sizes, it is found that while for most intermediate masses that we consider, the dark matter fraction comprising astrophysical $Q$-balls is at most subpercent, for other masses it may be significantly higher.

A recent assessment of the central compact object in the supernova remnant HESS $\mathrm{J}1731-347$ [Nat. Astron. 6, 1444 (2022)] reveals its remarkably small radius, accompanied by the intriguing characteristic of a mass smaller than one solar mass, a feature that has hitherto defied a conclusive explanation. To explain the astrophysical features of this peculiar source, in the present work, we consider two distinct dark matter models: the single-fluid dark matter model and the two-fluid dark matter model, both mixed within neutron stars. These two models can meet various astronomical observational constraints well and successfully account for the observational requirements of HESS $\mathrm{J}1731-347$. We further estimate the parameter space of these two dark matter classes in light of multimessenger observational constraints. Additionally, we investigate the effects of these dark matter models on tidal deformability, neutron star nonradial oscillation frequencies, and gravitational waves during the binary neutron star inspiral process. Our findings underscore the pivotal role played by dark matter in shaping the gravitational wave-related properties of neutron stars, thereby offering valuable insights for future observations.

Axionlike particles (ALPs) coupled to nucleons might be copiously emitted from a supernova (SN) core. We extend existing bounds on free-streaming ALPs to the case in which these are so strongly interacting with the nuclear matter to be trapped in the SN core. For strongly interacting ALPs, we also extend the bound from the absence of an ALP-induced signal in Kamiokande-II neutrino detector at the time of SN 1987A. We find that combining the different arguments, SNe exclude values of ALP-nucleon coupling $g_{aN}\gtrsim {10}^{-9}$ for ALP masses $m_a\lesssim 1\mathrm{MeV}$. Remarkably, in the case of canonical QCD axion models, the SN bounds exclude all values of $m_a\gtrsim {10}^{-2}\mathrm{eV}$. This result prevents the possibility for current and future cosmological surveys to detect any signatures due to hot dark matter QCD axion mass.

We revisit kinetic relaxation and soliton/boson star nucleation in fuzzy scalar dark matter featuring short-ranged self-interactions ${\mathcal{H}}_{\mathrm{int}}=-\lambda |\psi {|}^4/2m^2$, alongside gravitational self-interactions. We map out the full curve of nucleation timescale for both repulsive ($\lambda <0$) and attractive ($\lambda >0$) short-ranged self-interaction strength and in doing so reveal two new points. Firstly, besides the two usual terms, $\propto G^2$ and $\propto {\lambda }^2$, in the total relaxation rate ${\mathrm{\Gamma }}_{\text{relax}}$, there is an additional cross term $\propto G\lambda$ arising due to interference between gravitational and short-ranged self-interaction scattering amplitudes. This yields a critical repulsive interaction strength ${\lambda }_{\mathrm{cr}}\simeq -2\pi G{m}^2/v_0^2$, at which the relaxation rate is smallest and serves as the transition point between typical net attractive self-interaction ($\lambda \gtrsim {\lambda }_{\mathrm{cr}}$) and net repulsive self-interaction ($-\lambda \gtrsim -{\lambda }_{\mathrm{cr}}$). Secondly, while in the net attractive regime, nucleation timescale is similar to inverse relaxation timescale ${\tau }_{\mathrm{nuc}}\sim {\mathrm{\Gamma }}_{\text{relax}}^{-1}$; in the net repulsive regime, nucleation occurs at a delayed time ${\tau }_{\mathrm{nuc}}\sim (\lambda /{\lambda }_{\mathrm{cr}}){\mathrm{\Gamma }}_{\text{relax}}^{-1}$. We confirm our analytical understanding by performing 3D field simulations with varying average mass density $\overline{\rho }$, box size $L$ and grid size $N$.

Due to an accidentally large $s$-wave scattering length, in a relatively wide range of energy, neutrons are approximately described by the nonrelativistic conformal field theory of unitarity fermions, perturbed by one relevant and an infinite number of irrelevant operators. We develop a formalism which provides a nonperturbative definition of local operators in that nonrelativistic conformal field theory. We compute the scattering-length and effective-range corrections to the two-point functions of primary charge-three operators using the technique of conformal perturbation theory. These calculations allow us to find the first corrections to the scale-invariant behavior of the rate of nuclear reactions with three neutrons in the final state in the regime when the neutrons have small relative momenta.

We show that a new leptophilic Higgs sector can resolve some intriguing anomalies in current experimental data across multiple energy ranges. Motivated by the recent CMS excess in the resonant $e\mu$ channel at 146 GeV, we consider a leptophilic two-Higgs-doublet model, and propose a novel resonant production mechanism for the neutral components of the second Higgs doublet at the LHC using the lepton content of the proton. Interestingly, the same Yukawa coupling $Y_{e\mu }\sim 0.65–0.81$ that explains the CMS excess also addresses the muon ($g-2$) anomaly. Moreover, the new Higgs doublet also resolves the recent CDF $W$-boson mass anomaly. The relevant model parameter space will be completely probed by future LHC data.

We investigate a simple extension of the standard model in which the dark matter consists of a feebly interacting fermion, charged under a new $Z_4$ symmetry, that is produced in the early Universe by the freeze-in mechanism. The only other new particle included in the model is a singlet scalar, also charged under the $Z_4$, which couples to the fermion via Yukawa interactions and to the standard model Higgs. The model is truly minimal, as it admits just five free parameters: two masses and three dimensionless couplings. Depending on their values, the freeze-in mechanism can be realized in different ways, each characterized by its own production processes. For all of them, we numerically study the relic density as a function of the free parameters of the model and determine the regions consistent with the dark matter constraint. Our results show that this scenario is viable over a wide range of couplings and dark matter masses. This model, therefore, not only offers a novel solution to the dark matter problem, but it also provides a minimal realization of freeze-in for fermion dark matter.

We consider the type-II seesaw model extended with another Higgs doublet, which is odd under the $Z_2$ symmetry. We look for the possibility of triggering the electroweak symmetry breaking via radiative effects. The Higgs mass parameter changes sign from being positive at higher-energy scales to negative at lower-energy scales in the presence of the TeV scalar triplet. The Planck scale perturbativity is demanded and the electroweak phase transition is studied using two-loop $\beta$-functions. The maximum allowed values for the interaction quartic coupling of the second doublet field and the triplet field with the Higgs field are ${\lambda }_3=0.15$ and ${\lambda }_{{\mathrm{\Phi }}_{1\mathrm{\Delta }}}=0.50$, respectively. Considering these EW values, the first-order phase transition, i.e., ${\varphi }_{+}(T_c)/T_c\sim 0.6$ is satisfied only for vanishing doublet and triplet bare mass parameters, $m_{{\mathrm{\Phi }}_2}=0.0\mathrm{GeV}$ and $m_{\mathrm{\Delta }}=0.0\mathrm{GeV}$. The small nonzero induced vacuum expectation value for the scalar triplet also generates the neutrino mass, and the lightest stable neutral particle from the inert doublet satisfies the dark matter constraints for the chosen parameter space. The impact of the thermal corrections on the stability of the electroweak vacuum is also studied, and the current experimental values of the Higgs mass and the top mass lie in the stable region both at the zero temperature and the finite temperature.