Decoupled hidden sectors can easily and generically result in a period of cannibal domination, during which the dominant component of the Universe has an equation of state intermediate between radiation and matter due to self-heating by number-changing interactions. We present for the first time the consequences of a cannibal-dominated era prior to big bang nucleosynthesis for structure formation on small scales. We find that an early cannibal-dominated era imprints a characteristic peak on the dark matter power spectrum, with scale and amplitude directly determined by the mass, lifetime, and number-changing interaction strength of the cannibal field. This enhancement to the small-scale matter power spectrum will generate early-forming dark matter microhalos, and we provide a detailed and transparent map between the properties of the cannibal species and the characteristic mass and formation time of these structures. These relations demonstrate how the internal workings of a hidden sector leave a potentially observable imprint on the matter power spectrum even if dark matter has no direct couplings to the Standard Model.

The shape of the longitudinal development of the showers generated in the atmosphere by very high-energy cosmic ray particles encodes information about the mass composition of the flux, and about the properties of hadronic interactions that control the shower development. Studies of the shape of the depth of maximum distributions of showers with $E\gtrsim {10}^{17.3}\mathrm{eV}$ measured by the Pierre Auger Observatory, suggest, on the basis of a comparison with current models, that the composition of the cosmic ray flux undergoes a very important evolution, first becoming lighter and then rapidly heavier. These conclusions, if confirmed, would have profound and very surprising implications for our understanding of the high-energy astrophysical sources. Studies of the shape of the depth of maximum distribution in the same energy range have been used by the Auger and Telescope Array Collaboration to measure the interaction length of protons in air, a quantity that allows to estimate the $pp$ cross sections for values of $\sqrt{s}$ well above the LHC range. In this paper we argue that it is desirable to combine in a self-consistent way the studies of the cosmic ray composition with those aimed at the measurement of the $p$-air cross section. The latter necessarily provide information on both the fraction of protons in the flux and the properties of the showers generated by protons, that can be of great help in decoding the cosmic ray composition and in constraining the models of air shower development. At the same time a good determination of the cosmic ray composition, in particular of the helium component, is essential to infer correctly from the data the proton-air cross section.

In this work, we show that detecting the polarization information of ${\chi }_{cJ}\to \varphi \varphi (J=0,1,2)$ could be a practical way to test the hadronic loop effect in these decays. Our results show that the predicted ratios of helicity amplitudes are less dependent on the parameters involved in the calculation. The ratios are determined to be $|F_{1,1}^{(0)}/F_{0,0}^{(0)}|\approx 0.359$, $|F_{1,0}^{(1)}/F_{0,1}^{(1)}|=1$, $|F_{1,1}^{(1)}/F_{0,1}^{(1)}|=0$, $|F_{1,0}^{(2)}|/|F_{0,0}^{(2)}|=|F_{0,1}^{(2)}|/|F_{0,0}^{(2)}|\approx 1.285$, $|F_{1,-1}^{(2)}|/|F_{0,0}^{(2)}|=|F_{-1,1}^{(2)}|/|F_{0,0}^{(2)}|\approx 5.110$, and $|F_{-1,-1}^{(2)}|/|F_{0,0}^{(2)}|=|F_{1,1}^{(2)}|/|F_{0,0}^{(2)}|\approx 0.465$. By adopting these predicted ratios, we use the Monte Carlo events to show that the moments $⟨t_{ij}⟩$ can be used as observables to reveal the polarization transfer in these decays, and their distributions are directly related to the determination of helicity amplitudes. We suggest experiments like at the BESIII and the Belle II performing a polarization analysis on the ${\chi }_{cJ}\to \varphi \varphi$ decay in the future, and the results are important to understand the decay mechanism underlying the ${\chi }_{cJ}$ decays.

Models where dark matter is a part of an electroweak multiplet feature charged particles with macroscopic lifetimes due to the charged-neutral mass split of the order of pion mass. At the Large Hadron Collider, the ATLAS and CMS experiments will identify these charged particles as disappearing tracks, since they decay into a massive invisible dark matter candidate and a very soft charged Standard-Model particle, which fails to pass the reconstruction requirements. While ATLAS and CMS have focused on the supersymmetric versions of these scenarios, we have performed here the reinterpretation of the latest ATLAS disappearing track search for a suite of dark matter multiplets with different spins and electroweak quantum numbers. More concretely, we consider the cases of the inert two Higgs doublet, minimal fermion dark matter and vector triplet dark matter models. Our procedure is validated by using the same wino and Higgsino benchmark models employed by the ATLAS Collaboration. We have found that with the disappearing track signature, one can probe a vast portion of the parameter space, well beyond the reach of prompt missing energy searches (notably monojets). We provide tables with the upper limits on the cross section and efficiencies in the lifetime—a dark matter mass plane for all the models under consideration, which can be used for an easy recast for similar classes of models. Moreover, we provide the recasting code employed here, as part of the public LLP recasting repository.

The mass components of charmoniumlike states are investigated through the decomposition of QCD energy-momentum tensor (EMT) on lattice. The quark mass contribution $⟨H_m⟩$ and the momentum fraction $⟨x⟩$ of valence charm quark and antiquark are calculated for conventional $1S$, $1P$, $1D$ charmonia and the exotic $1^{-+}$ charmoniumlike state, based on the $N_f=2+1$ gauge configurations generated by the RBC/UKQCD collaboration. It is found that $⟨H_m⟩$ is close to each other and around 2.0 to 2.2 GeV for these states, which implies that the mass splittings among these states come almost from the gluon contribution of QCD trace anomaly. The $⟨x⟩$ of the $1^{-+}$ state is only around 0.55, while that in conventional charmonia is around 0.7 to 0.8. This difference manifests that the proportion of light quarks and gluons in the $1^{-+}$ charmoniumlike state is significantly larger than conventional states.

We study the real-time evolution of SU(2) Yang-Mills theory in a ($3+1$)-dimensional small lattice system after interaction quench. We numerically solve the Schrödinger equation with the Kogut-Susskind Hamiltonian in the physical Hilbert space obtained by solving Gauss law constraints. We observe the thermalization of a Wilson loop to the canonical state; the relaxation time is insensitive to the coupling strength and estimated as ${\tau }_{\mathrm{eq}}\sim 2\pi /T$ with temperatures $T$ at steady states. We also compute the vacuum persistence probability (the Loschmidt echo) to understand the relaxation from the dynamics of the wave function.

We investigate relativistic corrections of an order $1/m^2$, where $m$ is the constituent quark mass, to heavy baryon decays by emitting one pseudoscalar meson in the quark model. This work is motivated by shortcomings in the previous studies in the nonrelativistic quark model for decays of the Roper-like states, such as ${\mathrm{\Lambda }}_c(2765)$. We find that the relativistic corrections due to the internal motion of quarks are essential ingredients in improving their decay properties, such that the decay widths are significantly increased. In addition, such corrections can explain a phenomenological suppression of the quark axial-vector coupling constant $g_A^q$ for the ${\mathrm{\Sigma }}_c(2455)$ and ${\mathrm{\Sigma }}_c(2520)$ decays.

Bouncing models are alternatives to inflationary cosmology that replace the initial big bang singularity by a “bouncing” phase. A deeper understanding of the initial conditions of the universe, in these scenarios, requires knowledge of quantum aspects of bouncing models. In this work, we propose two classes of bouncing models that can be studied with great analytical ease and hence, provide a test bed for investigating more profound problems in quantum cosmology of bouncing universes. Our model’s two key ingredients enable us to do straightforward analytical calculations: (i) a convenient parametrization of the minisuperspace of FRLW spacetimes and (ii) two distinct choices of the effective perfect fluids that source the background geometry of the bouncing universe. We study the quantum cosmology of these models using both the Wheeler-de Witt equations and the path integral approach. In particular, we found a bouncing model analogue of the no-boundary wave function and presented a Lorentzian path integral representation for the same. We also discuss the introduction of real scalar perturbations.

We propose a covariant scheme for measuring entanglement on general hypersurfaces in relativistic quantum field theory. For that, we introduce an auxiliary relativistic field, “the discretizer,” that by locally interacting with the field along a hypersurface, fully swaps the field’s and discretizer’s states. It is shown, that the discretizer can be used to effectively cut off the field’s infinities, in a covariant fashion, and without having to introduce a spatial lattice. This, in turn, provides us an efficient way to evaluate entanglement between arbitrary regions on any hypersurface. As examples, we study the entanglement between complementary and separated regions in $1+1$ dimensions, for flat hypersurfaces in Minkowski space, for curved hypersurfaces in Milne space, and for regions on hypersurfaces approaching null-surfaces. Our results show that the entanglement between regions on arbitrary hypersurfaces in $1+1$ dimensions depends only on the spacetime end points of the regions, and not on the shape of the interior. Our results corroborate and extend previous results for flat hypersurfaces.

In the context of the dynamics and stability of black holes in modified theories of gravity, we derive the Teukolsky equations for massless fields of all spins in general spherically symmetric and static metrics. We then compute the short-ranged potentials associated with the radial dynamics of spin 1 and spin $1/2$ fields, thereby completing the existing literature on spin 0 and 2. These potentials are crucial for the computation of Hawking radiation and quasinormal modes emitted by black holes. In addition to the Schwarzschild metric, we apply these results and give the explicit formulas for the radial potentials in the case of charged (Reissner–Nordström) black holes, higher-dimensional black holes, and polymerized black holes arising from loop quantum gravity. These results are, in particular, relevant and applicable to a large class of regular black hole metrics. The phenomenological applications of these formulas will be the subject of a companion paper.

The low-redshift velocity field is a unique probe of the growth of cosmic structure and gravity. We propose to use distances from gravitational wave (GW) detections, in conjunction with the redshifts of their host galaxies from wide field spectroscopic surveys (e.g., DESI, 4MOST, TAIPAN), to measure peculiar motions within the local Universe. Such measurement has the potential to constrain the growth rate $f{\sigma }_8$ and test gravity through determination of the gravitational growth index $\gamma$, complementing constraints from other peculiar velocity measurements. We find that binary neutron star mergers with associated counterpart at $z\lesssim 0.2$ that will be detected by the Einstein Telescope (ET) will be able to constrain $f{\sigma }_8$ to $\sim 3\%$ precision after 10 years of operations when combined with galaxy overdensities from DESI and TAIPAN. If a larger network of third generation GW detectors is available (e.g., including the Cosmic Explorer), the same constraints can be reached over a shorter timescale ($\sim 5\mathrm{years}$ for a 3 detectors network). The same events (plus information from their hosts’ redshifts) can constrain $\gamma$ to ${\sigma }_{\gamma }\lesssim 0.04$. This constraint is precise enough to discern general relativity from other popular gravity models at $3\sigma$. This constraint is improved to ${\sigma }_{\gamma }\sim 0.02–0.03$ when combined with galaxy overdensities. The potential of combining galaxies’ peculiar velocities with gravitational wave detections for cosmology highlights the need for extensive optical to near-infrared follow-up of nearby gravitational wave events, or exquisite GW localization, in the next decade.

Early dark energy, as a proposed solution to the Hubble tension, faces an additional “why now” problem. Why should dark energy emerge just prior to recombination, billions of years before the onset of cosmic acceleration? Assisted quintessence explains this connection by positing that multiple scaling fields build up over time to drive the present-day cosmic acceleration. In this framework, early dark energy is inevitable. Yet, we show that scaling also leads to the demise of the scenario: the same feature that solves the coincidence problem then spoils a concordance of the Hubble constant inferred from the cosmic microwave background with that from the local distance ladder. The failure of the model offers a novel lesson on the ability of new physics to resolve the Hubble tension.

Berry’s phase, which is associated with the slow cyclic motion with a finite period, looks like a Dirac monopole when seen from far away but smoothly changes to a dipole near the level crossing point in the parameter space in an exactly solvable model. This topology change of Berry’s phase is visualized as a result of the lensing effect; the monopole supposed to be located at the level crossing point appears at the displaced point when the variables of the model deviate from the precisely adiabatic movement. The effective magnetic field generated by Berry’s phase is determined by a simple geometrical consideration of the magnetic flux coming from the displaced Dirac monopole.

We show that using renormalization-group summation to generate the QCD radiative corrections to the $\pi -\gamma$ transition form factor, calculated with light-cone sum rules (LCSR), renders the strong coupling free of Landau singularities while preserving the QCD form-factor asymptotics. This enables a reliable applicability of the LCSR method to momenta well below $1{\mathrm{GeV}}^2$. This way, one can use the new preliminary BESIII data with unprecedented accuracy below $1.5{\mathrm{GeV}}^2$ to fine tune the prefactor of the twist-six contribution. Using a combined fit to all available data below $3.1{\mathrm{GeV}}^2$, we are able to determine all nonperturbative scale parameters and a few Gegenbauer coefficients entering the calculation of the form factor. Employing these ingredients, we determine a pion distribution amplitude with conformal coefficients $(b_2,b_4)$ that agree at the $1\sigma$ level with the data for $Q^2\le 3.1{\mathrm{GeV}}^2$ and fulfill at the same time the lattice constraints on $b_2$ at ${\mathrm{N}}^3\mathrm{LO}$ together with the constraints from QCD sum rules with nonlocal condensates. The form-factor prediction calculated herewith reproduces the data below $1{\mathrm{GeV}}^2$ significantly better than analogous predictions based on a fixed-order power-series expansion in the strong coupling constant.

We investigate the sensitivity of the projected TeV muon collider to the gauged $L_{\mu }-L_{\tau }$ model. Two processes are considered: $Z^{\prime }$-mediated two-body scatterings ${\mu }^{+}{\mu }^{-}\to {\ell }^{+}{\ell }^{-}$ with $\ell =\mu$ or $\tau$ and scattering with initial state photon emission, ${\mu }^{+}{\mu }^{-}\to \gamma Z^{\prime },Z^{\prime }\to \ell \overline{\ell }$, where $\ell$ can be $\mu$, $\tau$, or ${\nu }_{\mu /\tau }$. We quantitatively study the sensitivities of these two processes by taking into account possible signals and relevant backgrounds in a muon collider experiment with a center-of-mass energy $\sqrt{s}=3\mathrm{TeV}$ and a luminosity $L=1{\mathrm{ab}}^{-1}$. For two-body scattering, one can exclude $Z^{\prime }$ masses $M_{Z^{\prime }}\lesssim 100\mathrm{TeV}$ with $\mathcal{O}(1)$ gauge couplings. When $M_{Z^{\prime }}\lesssim 1\mathrm{TeV}<\sqrt{s}$, one can exclude $g^{\prime }\gtrsim 2\times {10}^{-2}$. The process with photon emission is more powerful than the two-body scattering if $M_{Z^{\prime }}<\sqrt{s}$. For instance, a sensitivity of $g^{\prime }\simeq 4\times {10}^{-3}$ can be achieved at $M_{Z^{\prime }}=1\mathrm{TeV}$. The parameter spaces favored by the $(g-2{)}_{\mu }$ and $B$ anomalies with $M_{Z^{\prime }}>100\mathrm{GeV}$ are entirely covered by a muon collider.

We derive the effective Hamiltonian describing collective oscillations of Majorana neutrinos with a transition magnetic moment, allowing for the presence of scalar and pseudoscalar nonstandard neutrino self-interactions (NSSIs). Using this Hamiltonian, we analyze new flavor instability channels of collective oscillations in a core-collapse supernova environment that open up in the presence of a small but nonzero neutrino magnetic moment. It turns out that, contrary to certain claims in the literature, within the minimally extended Standard Model (i.e., without NSSIs), no new instabilities arise within the linear order, nor do they produce any observable signatures in the neutrino flavor-energy spectra, at least for magnetic moments up to ${10}^{-15}{\mu }_{\mathrm{B}}$ and quite realistic fields of the order of ${10}^{12}\mathrm{Gauss}$. On the other hand, in the presence of NSSIs, new fast and slow instabilities mixing neutrinos and antineutrinos appear, which show up in the spectra even for tiny magnetic moments of the order of ${10}^{-24}{\mu }_{\mathrm{B}}$, leading to considerable distortions of the spectra and nonstandard spectral splits. We study sensitivity of collective oscillations to these, NSSI-induced instabilities in detail and discuss the observability of the NSSI couplings triggering them.

We study the cross sections for the inclusive production of $\psi (2S)$ and $X(3872)$ hadrons in $pp$ collisions at the LHC at two different center-of-mass energies and compare them with experimental data obtained by the ATLAS, CMS, and LHCb Collaborations.

In this work, we investigate not only the pole masses but also the screening masses of neutral pions at finite temperature and magnetic field by utilizing the random phase approximation (RPA) approach in the framework of the two-flavor Nambu–Jona-Lasinio model. And two equivalent formalisms in the presence of a magnetic field, i.e., the Landau level representation and the proper-time representation (PTR), are applied to obtain the corresponding analytical expressions of the polarization functions (except the expressions for the pole masses in the PTR). In order to evaluate the applicable region of the low-momentum expansion (LME), we compare the numerical results within the full RPA (FRPA) with those within the reduced RPA, i.e., the RPA in the LME. It is confirmed that the pole masses of ${\pi }^0$ in the FRPA suffer a sudden mass jump at the Mott transition temperature when in the presence of external magnetic field, the Mott transition temperature is catalyzed by the magnetic field. And by analyzing the behaviors of the directional sound velocities of ${\pi }^0$, which are associated with the breaking of the Lorentz invariance by the heat bath and the magnetic field, we clarify the two problems existing in previous literatures: one is that the transverse sound velocities in the medium are always larger than unity and thus violate the law of causality on account of the noncovariant regularization scheme, and the other is that the longitudinal sound velocities are identically equal unity at finite temperature on account of the limitation of the derivative expansion method used.

Neutrino-nucleus elastic scattering ($\nu {\mathrm{A}}_{el}$) provides a unique laboratory to study the quantum-mechanical (QM) coherency effects in electroweak interactions. The deviations of the cross sections from those of completely coherent systems can be quantitatively characterized through a coherency parameter $\alpha (q^2)$. The relations between $\alpha$ and the underlying nuclear physics in terms of nuclear form factors are derived. The dependence of cross section on $\alpha (q^2)$ for the various neutrino sources is presented. The $\alpha (q^2)$ values are evaluated from the measured data of the COHERENT CsI and Ar experiments. Complete coherency and decoherency conditions are excluded by the CsI data with $p=0.004$ at $q^2=3.1\times {10}^3{\mathrm{MeV}}^2$ and $p=0.016$ at $q^2=2.3\times {10}^3{\mathrm{MeV}}^2$, respectively, verifying that both QM superpositions and nuclear many-body effects contribute to $\nu {\mathrm{A}}_{el}$ interactions.

$\mathrm{U}(N)$ supersymmetric Yang-Mills theory naturally appears as the low-energy effective theory of a system of $N$ D-branes and open strings between them. Transverse spatial directions emerge from scalar fields, which are $N\times N$ matrices with color indices; roughly speaking, the eigenvalues are the locations of D-branes. In the past, it was argued that this simple “emergent space” picture cannot be used in the context of gauge/gravity duality, because the ground-state wave function delocalizes at large $N$, leading to a conflict with the locality in the bulk geometry. In this paper, we show that this conventional wisdom is not correct: the ground-state wave function does not delocalize, and there is no conflict with the locality of the bulk geometry. This conclusion is obtained by clarifying the meaning of the “diagonalization of a matrix” in Yang-Mills theory, which is not as obvious as one might think. This observation opens up the prospect of characterizing the bulk geometry via the color degrees of freedom in Yang-Mills theory, all the way down to the center of the bulk.