The standard model (SM) has several issues related to the $CP$ violation which could give clues to search physics beyond the SM. They are a $CP$ phase in the Cabibbo-Kobayashi-Maskawa matrix, the strong $CP$ problem, $CP$ phases in the Pontecorvo-Maki-Nakagawa-Sakata matrix, and $CP$ asymmetry in lepton-number-violating processes related to baryon number asymmetry. We consider a model which could give a unified explanation for them in a framework of spontaneous $CP$ violation. It is an extension of the SM with vectorlike fermions and singlet scalars. In this model, they are explained by a common complex phase caused in the spontaneous $CP$ violation. We present concrete examples for them and also discuss some relevant phenomenology.

Dark photons can oscillate into Standard Model (SM) photons via kinetic mixing. The conversion probability depends sensitively on properties of the ambient background, such as the density and electromagnetic field strength, which cause the SM photon to acquire an in-medium effective mass. Resonances can enhance the conversion probability when there is a level-crossing between the dark photon and background-dependent SM photon states. In this work, we show that the widely used Landau-Zener (LZ) approximation breaks down when there are multiple level-crossings due to a nonmonotonic SM photon potential. Phase interference effects, especially when the dark photon mass is close to an extremum of the SM photon effective mass, can cause deviations from the LZ approximation at the level of a few orders of magnitude in the conversion probability. We present an analytic approximation that is valid in this regime and that can accurately predict the conversion probabilities in a wide range of astrophysical environments.

The neutral pion generates the leading pole contribution to the hadronic light-by-light tensor, which is given in terms of the nonperturbative transition form factor ${\mathcal{F}}_{{\pi }^0\gamma \gamma }(q_1^2,q_2^2)$. Here we present an ab-initio lattice calculation of this quantity in the continuum and at the physical point using twisted-mass lattice QCD. We report our results for the transition form factor parametrized using a model-independent conformal expansion valid for arbitrary spacelike kinematics and compare it with experimental measurements of the single-virtual form factor, the two-photon decay width, and the slope parameter. We then use the transition form factors to compute the pion-pole contribution to the hadronic light-by-light scattering in the muon $g-2$, finding $a_{\mu }^{{\pi }^0-\mathrm{pole}}=56.7(3.2)\times {10}^{-11}$.

Quantum simulations of lattice gauge theories are anticipated to directly probe the real time dynamics of QCD, but scale unfavorably with the required truncation of the gauge fields. Improved Hamiltonians are derived to correct for the effects of gauge field truncations on the SU(3) Kogut-Susskind Hamiltonian. It is shown in $1+1D$ that this enables low chromoelectric field truncations to quantitatively reproduce features of the untruncated theory over a range of couplings and quark masses. In $3+1D$, an improved Hamiltonian is derived for lattice QCD with staggered massless fermions. It is shown in the strong coupling limit that the spectrum qualitatively reproduces aspects of two flavor QCD and simulations of a small system are performed on IBM’s Perth quantum processor.

The Sachdev-Ye-Kitaev (SYK) model shows chaotic behavior with a maximal Lyapunov exponent. In this paper, we investigate the four-point function of a SYK-type model numerically, which gives us access to its Lyapunov exponent. The model consists of two sets of Majorana fermions, called A and B, and the interactions are restricted to being exclusively pairwise between the two sets, not within the sets. We find that the Lyapunov exponent is still maximal at strong coupling. Furthermore, we show that even though the conformal dimensions of the A and B fermions change with the population ratio, the Lyapunov exponent remains constant, not just in the conformal limit where it is maximal, but also in the intermediate and weak coupling regimes.

With the assumptions that the $T_{cc}^{+}$ discovered at LHCb is a $D^{*}D$ hadronic molecule, using a nonrelativistic effective field theory we calculate the radiative partial widths of $T_{cc}^{*}\to D^{*}D\gamma$ with $T_{cc}^{*}$ being a $D^{*}{D}^{*}$ shallow bound state and the heavy-quark-spin partner of $T_{cc}^{+}$. The $I=0$ $D^{*}D$ rescattering effect with the $T_{cc}$ pole is taken into account. The results show that the isoscalar $D^{*}D$ rescattering can increase the tree-level decay width of $T_{cc}^{*+}\to D^{*+}{D}^0\gamma$ by about 50% and decrease that of $T_{cc}^{*+}\to D^{*0}{D}^{+}\gamma$ by a similar amount. The two-body partial decay widths of the $T_{cc}^{*+}$ into $T_{cc}^{+}\gamma$ and $T_{cc}^{+}{\pi }^0$ are also calculated, and the results are about 6 and 3 keV, respectively. Considering that the $D^{*}$ needs to be reconstructed from the $D\pi$ or $D\gamma$ final state in an experimental measurement, the four-body partial widths of the $T_{cc}^{*+}$ into $DD\gamma \gamma$ and $DD\pi \gamma$ are explicitly calculated, and we find that the interference effect between different intermediate $D^{*}D\gamma$ states is small. The total radiative decay width of the $T_{cc}^{*}$ is predicted to be about 24 keV. Adding the hadronic decay widths of $T_{cc}^{*}\to D^{*}D\pi$, the total width of the $T_{cc}^{*}$ is finally predicted to be $(65\pm 2)\mathrm{keV}$.

The gravitational form factors of a hadron are defined through the matrix elements of the energy-momentum tensor current, which can be decomposed into the quark and gluonic parts, between the hadronic states. These form factors provide important information for answering fundamental questions about the distribution of the energy, the spin, the pressure, and the shear forces inside the hadrons. Theoretical and experimental studies of these form factors provide exciting insights on the inner structure and geometric shapes of hadrons. Inspired by this, the gravitational form factors of $\mathrm{\Delta }$ resonance are calculated by employing the QCD sum rule approach. The acquired gravitational form factors are used to calculate the composite gravitational form factors like the energy and angular momentum multipole form factors, D-terms related to the mechanical properties like the internal pressure and shear forces, as well as the mass radius of the system. The predictions are compared with the existing results in the literature.

In this work, we investigate the decay behaviors of several higher strangeonia into $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ through a hadronic-loop mechanism, enabling us to predict some physical observables, including the branching ratios. Furthermore, we assess the reliability of our research by successfully reproducing experimental data related to the cross section of $e^{+}{e}^{-}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ interactions. In this context, we account for the contributions arising from higher strangeonia, specifically $\varphi (4S)$ and $\varphi (3D)$. Additionally, we extend this study to encompass higher strangeonia decays into other light flavor baryon pairs, such as $\mathrm{\Sigma }\overline{\mathrm{\Sigma }}$ and $\mathrm{\Xi }\overline{\mathrm{\Xi }}$. By employing the same mechanism, we aim to gain valuable insights into the decay processes involving these particles. By conducting this investigation, we hope to shed light on the intricate decay mechanisms of higher strangeonia and their interactions with various baryons pairs.

When neutrinos are propagating in ordinary matter, their coherent forward scattering off background particles results in the so-called Mikheyev-Smirnov-Wolfenstein (MSW) matter potential, which plays an important role in neutrino flavor conversions. In this paper, we present a complete one-loop calculation of the MSW matter potential in the Standard Model. First, we carry out the one-loop renormalization of the Standard Model in the on-shell scheme, where the electromagnetic fine-structure constant $\alpha$, the weak gauge-boson masses $m_W$ and $m_Z$, the Higgs-boson mass $m_h$ and the fermion masses $m_f$ are chosen as input parameters. Then, the finite corrections to the scattering amplitudes of neutrinos with the electrons and quarks are calculated, and the one-loop MSW matter potentials are derived. Adopting the latest values of all physical parameters, we find that the relative size of one-loop correction to the charged-current matter potential of electron-type neutrinos or antineutrinos turns out to be 6%, whereas that to the neutral-current matter potential of all-flavor neutrinos or antineutrinos can be as large as 8%. The calculations are also performed in the $\overline{\text{MS}}$ scheme and compared with previous results in the literature.

Based on $(2712.4\pm 14.3)\times {10}^6$ events recorded at the $\psi (3686)$ nominal mass collected with the BESIII detector operating at the BEPCII collider, the $\psi (3686)\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}\omega$ and ${\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}\varphi$ decays are observed for the first time with statistical significances of $13.8\sigma$ and $7.6\sigma$, respectively. The corresponding branching fractions are measured to be $\mathcal{B}(\psi (3686)\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}\omega )=(1.89\pm 0.18\pm 0.21)\times {10}^{-5}$ and $\mathcal{B}(\psi (3686)\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}\varphi )=(2.96\pm 0.54\pm 0.41)\times {10}^{-6}$, where the first uncertainties are statistical and the second systematic.

A search for a new pseudoscalar $a$-boson produced in events with a top-quark pair, where the $a$-boson decays into a pair of muons, is performed using $\sqrt{s}=13\mathrm{TeV}$ $pp$ collision data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of $139{\mathrm{fb}}^{-1}$. The search targets the final state where only one top quark decays to an electron or muon, resulting in a signature with three leptons $e\mu \mu$ and $\mu \mu \mu$. No significant excess of events above the Standard Model expectation is observed and upper limits are set on two signal models: $pp\to t\overline{t}a$ and $pp\to t\overline{t}$ with $t\to H^{\pm }b$, $H^{\pm }\to W^{\pm }a$, where $a\to \mu \mu$, in the mass ranges $15\mathrm{GeV}<m_a<72\mathrm{GeV}$ and $120\mathrm{GeV}\le m_{H^{\pm }}\le 160\mathrm{GeV}$.

The free propagator of a massless mode in an expanding universe can be written as a sum of two terms, a light cone and a tail part. The latter describes a subluminal (timelike) signal. We show that the inflationary gravitational wave background, influencing cosmic microwave background polarization and routinely used for constraining inflationary models through the so-called $r$ ratio, originates exclusively from the tail part.

We perform the first simultaneous extraction of parton collinear and transverse degrees of freedom from low-energy fixed-target Drell-Yan data in order to compare the transverse momentum dependent (TMD) parton distribution functions (PDFs) of the pion and proton. We demonstrate that the transverse separation of the quark field encoded in TMDs of the pion is more than $4\sigma$ smaller than that of the proton. Additionally, we find the transverse separation of the quark field decreases as its longitudinal momentum fraction decreases. In studying the nuclear modification of TMDs, we find clear evidence for a transverse EMC effect. We comment on possible explanations for these intriguing behaviors, which call for a deeper examination of tomography in a variety of strongly interacting quark-gluon systems.

An important conjecture within the $\mathrm{AdS}/\mathrm{CFT}$ correspondence relates holographic spacetime to the quantum computational complexity of the dual quantum field theory. However, the quantitative understanding of this relation is largely an open question. In this work, to address this question we establish a map between a computational complexity measure and its holographic counterpart from first principles. We consider quantum circuits built out of conformal transformations in two-dimensional conformal field theory and a complexity measure based on assigning a cost to quantum gates via the Fubini-Study distance. We find a novel geometric object in three-dimensional anti–de Sitter spacetimes that is dual to this distance. This duality also provides a more general map between holographic geometry of anti–de Sitter universes and complexity geometry as defined in information theory, in which each point represents a state and distances between states are measured by the Fubini-Study metric. We apply the newly found duality to the eternal black hole spacetime and discuss both the origin of linear growth of complexity and the switchback effect within our approach.

Investigating the quantum nature of gravity is an important issue in modern physics. Recently, studies pertaining to the quantum superposition of gravitational potential have garnered significant interest. Inspired by Mari et al. [Sci. Rep. 6, 22777 (2016)] and Baym and Ozawa [Proc. Natl. Acad. Sci. U.S.A. 106, 3035 (2009)], Belenchia et al. [Phys. Rev. D 98, 126009 (2018)] considered a gedanken experiment involving such a quantum superposition and mentioned that the superposition renders causality and complementarity inconsistent. They resolved this inconsistency by considering the quantized dynamical degrees of freedom of gravity. This suggests a strong relationship between the quantum superposition of the gravitational potential and the quantization of the gravitational field. In our previous study [Phys. Rev. D 106, 125002 (2022)], we have shown that the quantum uncertainty of a field guarantees the consistency between causality and complementarity. In this study, we focus on the entanglement between two particles’ states due to the electromagnetic/gravitational potential and investigate its relationship with quantum uncertainty, causality, and complementarity. Our numerical analyses show that the quantum uncertainty of the electromagnetic/gravitational field results in vacuum fluctuations and prohibits the entanglement between two particles’ states when causality is satisfied. We further demonstrate that complementarity holds when the particles do not get entangled. The uncertainty relation does not cause the entanglement between two particles’ states, which guarantees complementarity.

We investigate the correlation harvesting protocol using two Unruh-DeWitt particle detectors moving along four classes of uniformly accelerated trajectories categorized by Letaw: linear, catenary, cusped, and circular motions. For each trajectory, two types of configurations are carried out: one possesses a stationary (time-translation invariant) Wightman function and the other is nonstationary. We find that detectors undergoing linear, catenary, and cusped motions gain fewer correlations in the nonstationary configurations compared to those in stationary configurations. Detectors in circular motion have similar behavior in both configurations. We discuss the relative suppression of correlation harvesting due to high acceleration for each case. Remarkably we find that under certain circumstances detectors in both linear and circular states of motion can harvest genuine (non-communication-assisted) entanglement even though they are in causal contact.

We explore $T\overline{T}$ deformations of warped conformal field theories (WCFTs) in two dimensions as examples of $T\overline{T}$ deformed nonrelativistic quantum field theories. WCFTs are quantum field theories with a $\mathrm{Virasoro}\times \mathrm{U}(1)$ Kac-Moody symmetry. We compute the deformed symmetry algebra of a $T\overline{T}$ deformed holographic WCFT, using the asymptotic symmetries of ${\mathrm{AdS}}_3$ with $T\overline{T}$ deformed Compére, Song, and Strominger boundary conditions. The U(1) Kac-Moody symmetry survives provided one allows the boundary metric to transform under the asymptotic symmetry. The Virasoro sector remains but is now deformed and no longer chiral.

Based on the freely-falling Unruh-Dewitt model, we study the influence of gravitational waves on the quantum multibody states, i.e., the twin-Fock (TF) state and the mixture of Dicke states. The amount of entanglement of quantum many-body states decreases first and then increases with increasing frequency of gravitational waves. In particular, for some fixed frequencies of gravitational waves, entanglement will increase with the increasing amplitude of gravitational waves, which is different from the usual thought of gravity-induced decoherence and could provide a novel understanding for the quantum property of gravitational waves.

We study linear perturbations around a static and spherically symmetric black hole solution in spatially covariant gravity with just two tensorial degrees of freedom. In this theory, gravity modification is characterized by a single time-dependent function that appears in the coefficient of $K^2$ in the action, where $K$ is the trace of the extrinsic curvature. The background black hole solution is given by the Schwarzschild solution foliated by the maximal slices and has a universal horizon at which the lapse function vanishes. We show that the quadratic action for the odd-parity perturbations is identical to that in general relativity upon performing an appropriate coordinate transformation. This in particular implies that the odd-parity perturbations propagate at the speed of light, with the inner boundary being the usual event horizon. We also derive the quadratic action for even-parity perturbations. In the even-parity sector, one of the two tensorial degrees of freedom is mixed with an instantaneous scalar mode, rendering the system distinct from that in general relativity. We find that monopole and dipole perturbations, which are composed solely of the instantaneous scalar mode, have no solutions regular both at the universal horizon and infinity (except for the trivial one corresponding to the constant shift of the mass parameter). We also consider stationary perturbations with higher multipoles. By carefully treating the locations of the inner boundary, we show that also in this case there are no solutions regular both at the inner boundary and infinity. Thus, the black hole solution we consider is shown to be perturbatively unique.

Finsler spacetime geometry is a canonical extension of Riemannian spacetime geometry. It is based on a general length measure for curves (which does not necessarily arise from a spacetime metric) and it is used as an effective description of spacetime in quantum gravity phenomenology as well as in extensions of general relativity aiming to provide a geometric explanation of dark energy. A particular interesting subclass of Finsler spacetimes are those of Berwald type, for which the geometry is defined in terms of a canonical affine connection that uniquely generalizes the Levi-Civita connection of a spacetime metric. In this sense, Berwald Finsler spacetimes are Finsler spacetimes closest to pseudo-Riemannian ones. We prove that all Ricci-flat, spatially spherically symmetric Berwald spacetime structures are either pseudo-Riemannian (Lorentzian), or flat. This insight enables us to generalize the Jebsen-Birkhoff theorem to Berwald spacetimes.