In this article, we present a complete classification of the negative parity ${\mathrm{\Xi }}_{c/b}^{\prime }$ and ${\mathrm{\Xi }}_{c/b}$ $P$-wave states: seven belonging to the $SU(3)$ flavor sextet and seven to the flavor antitriplet, the calculation of the ${\mathrm{\Xi }}_{c/b}^{\prime }$ and ${\mathrm{\Xi }}_{c/b}$ strong partial decay widths into ${{}^2\mathrm{\Sigma }}_c\overline{K}$, ${{}^2\mathrm{\Xi }}_c^{\prime }\pi$, ${{}^4\mathrm{\Sigma }}_c\overline{K}$, ${{}^4\mathrm{\Xi }}_c^{\prime }\pi$, ${\mathrm{\Lambda }}_c^{\prime }\overline{K}$, ${\mathrm{\Xi }}_c\pi$, and ${\mathrm{\Xi }}_c\eta$ channels both within the elementary emission model and the ${}^3{P}_0$ model, and the calculation of the electromagnetic decay widths for ${\mathrm{\Xi }}_{c/b}^{\prime }$ and ${\mathrm{\Xi }}_{c/b}$ radiative decays. By means of the equal-spacing mass rule and by the analysis of the strong partial decay widths, we suggest possible assignments for the new LHCb ${\mathrm{\Xi }}_c(2923{)}^0$, ${\mathrm{\Xi }}_c(2939{)}^0$, and ${\mathrm{\Xi }}_c(2965{)}^0$ states, as well as for the ${\mathrm{\Xi }}_c$’s previously reported by Belle and BABAR. Our results can be tested by future experiments, at LHCb and Belle, disentangling the remaining missing piece of information, i.e., the quantum numbers. Finally, a comparison is made between a three-quark and a quark-diquark description of ${\mathrm{\Xi }}_c$ states. Very recently the LHCb Collaboration reported the observation of two new ${\mathrm{\Xi }}_b$ states, namely ${\mathrm{\Xi }}_b(6327{)}^0$ and ${\mathrm{\Xi }}_b(6333{)}^0$, in the ${\mathrm{\Lambda }}_b^0{K}^{-}{\pi }^{+}$ channel with a statistical significance larger than 9 standard deviations. The experimental masses and widths of these two states are consistent with our mass and width predictions for the doublet of $D$-wave excitations of the ${\mathrm{\Xi }}_b$ system with $J_{{\mathrm{\Xi }}_b(6327{)}^0}^P=3/2^{+}$ and $J_{{\mathrm{\Xi }}_b(6333{)}^0}^P=5/2^{+}$.

We propose a new mechanism of the heavy-quark spin polarization (HQSP) in quark matter induced by the Kondo effect under an external magnetic field. The Kondo effect is caused by a condensate between a heavy and a light quark called the Kondo condensate leading to a mixing of the heavy- and light-quark spins. Thus, the HQSP is driven through the Kondo effect from light quarks coupling with the magnetic field in quark matter. For demonstration, we employ the Nambu-Jona-Lasinio type model under a magnetic field and investigate the HQSP within the linear response theory with vertex corrections required by the $U(1{)}_{\mathrm{EM}}$ electromagnetic gauge invariance. As a result, we find that the HQSP arises significantly with the appearance of the Kondo effect. Our findings are testable in future sign-problem-free lattice simulations.

Electroweak interactions assign a central role to the gauge group $SU(2{)}_L\times U(1{)}_Y$, which is either realized linearly (SMEFT) or nonlinearly (e.g., HEFT) in the effective theory obtained when new physics above the electroweak scale is integrated out. Although the discovery of the Higgs boson has made SMEFT the default assumption, nonlinear realization remains possible. The two can be distinguished through their predictions for the size of certain low-energy dimension-6 four-fermion operators: for these, HEFT predicts $O(1)$ couplings, while in SMEFT they are suppressed by a factor $v^2/{\mathrm{\Lambda }}_{\mathrm{NP}}^2$, where $v$ is the Higgs vev. One such operator, $O_V^{LR}\equiv (\overline{\tau }{\gamma }^{\mu }{P}_L\nu )(\overline{c}{\gamma }_{\mu }{P}_{R}b)$, contributes to $b\to c{\tau }^{-}\overline{\nu }$. We show that present constraints permit its non-SMEFT coefficient to have a HEFTy size. We also note that the angular distribution in $\overline{B}\to D^{*}(\to D{\pi }^{\prime }){\tau }^{-}(\to {\pi }^{-}{\nu }_{\tau }){\overline{\nu }}_{\tau }$ contains enough information to extract the coefficients of all new-physics operators. Future measurements of this angular distribution can therefore tell us if non-SMEFT new physics is really necessary.

We study the weak radiative decays of ${\mathbf{B}}_b\to {\mathbf{B}}_n\gamma$ with ${\mathbf{B}}_{b(n)}$ the antitriplet bottomed (octet) baryons in the light-front quark model. We obtain that $\mathcal{B}({\mathrm{\Lambda }}_b\to \mathrm{\Lambda }\gamma )=(7.1\pm 0.3)\times {10}^{-6}$, which agrees well with the current experimental value of $(7.1\pm 1.7)\times {10}^{-6}$. We predict that $\mathcal{B}({\mathrm{\Xi }}_b^0\to {\mathrm{\Xi }}^0\gamma )=(1.0\pm 0.1)\times {10}^{-5}$ and $\mathcal{B}({\mathrm{\Xi }}_b^{-}\to {\mathrm{\Xi }}^{-}\gamma )=(1.1\pm 0.1)\times {10}^{-5}$, which are consistent with the latest upper limits set by the LHCb Collaboration. In addition, we find that the $SU(3{)}_F$ flavor symmetry breaking effects for the modes related to the $b\to d\gamma$ transition can be as large as 20%.

We examine the Tolman temperature by using Carter’s variational formalism of thermodynamics. We restrict our interests to fluids in thermal equilibrium that the heat does not propagate. We show that this condition presents a general formula for the local temperature gradient. We suggest a resolution of the recently addressed conflict in Tolman temperature when a chemical potential does not vanish.

A striking feature of the timelike nucleon electromagnetic form factors, investigated in $e^{+}{e}^{-}\to N\overline{N}$ annihilation reactions, is the modulation by local structures of small magnitude and oscillatory form, showing up above the $N\overline{N}$ threshold. Starting from an isospin decomposition of the proton and neutron form factors it is shown that such structures are the natural consequence of the interference of a large and a small amplitude, resulting in a sinusoidal behavior as a function of the “invariant energy” if the relative phase shift varies with energy. Thus, periodic oscillations superimposed on a smooth background will be observed. In this scenario, the equal size of the modulation for neutrons and protons (discovered by recent BESIII data) implies the particular isoscalar or isovector nature of these local structures, or their orthogonal interference. Hence, it specifies their origin as excited vector mesons whose widths are tied to the modulation frequency. We clarify that the phase difference of the modulation between neutrons and protons as BESIII data found, but not the modulation itself, is the evidence of an imaginary part of the timelike nucleon electromagnetic form factors, which is associated with the rescattering processes.

We present a stringy realization of quantum field theory ensembles in $D\le 4$ spacetime dimensions, thus realizing a disorder averaging over coupling constants. When each member of the ensemble is a conformal field theory with a standard semiclassical holographic dual of the same radius, the resulting bulk can be interpreted as a single asymptotically anti–de Sitter space geometry with a distribution of boundary components joined by wormhole configurations, as dictated by the Hartle–Hawking wave function. This provides a UV completion of a recent proposal by Marolf and Maxfield that there is a high-dimensional Hilbert space for baby universes, but one that is compatible with the proposed swampland constraints of McNamara and Vafa. This is possible because our construction is really an approximation that breaks down both at short distances, but also at low energies for objects with a large number of microstates. The construction thus provides an explicit set of counterexamples to various claims in the literature that holographic and effective field theory considerations can be reliably developed without reference to any UV completion.

There are several possible choices of the time parameter for the canonical description of a self-gravitating thin shell, but quantum theories built on different time parameters lead to unitarily inequivalent descriptions. We compare the quantum collapse of a thin dust shell in two different times viz., the time coordinate in the interior of the shell (originally addressed by Hajiček, Kay and Kuchař [Phys. Rev. D 46, 5439 (1992)]) and the time coordinate of the comoving observer (proper time). In each case, we obtain exact solutions to the Wheeler-DeWitt equation requiring only a finite and well-behaved $U(1)$ current. The two quantum theories are complementary and each highlights the role played by the Planck mass: stationary states of positive energy in interior time exist only if the shell rest mass is smaller than the Planck mass. In proper time they exist only when the shell rest mass is greater than the Planck mass. In coordinate time there are both scattering states and bound states with a well-defined energy spectrum. In the proper time description there are only bound states, whose spectrum we determine.

In this work we numerically explore the quantum behavior of a classically unstable relativistic Bose-Einstein condensate (BEC). The main goal is to study the phenomenon of so-called quantum break time which amounts to a significant departure from a semiclassical mean-field description. It has been suggested previously that the existence of Lyapunov instability is crucial for a fast quantum breaking, chaos and scrambling. In order to clarify the issue, we work within the 2-PI effective action formalism and introduce a simple and very widely applicable dynamical criterion for identifying the timescale of quantum breaking. We indeed observe that the fast quantum break time is controlled by the Lyapunov exponent of the unstable BEC.

A program of wide interest in modern conformal bootstrap studies is to numerically solve general conformal field theories, based on a critical assumption that the dynamics is encoded in the conformal four-point crossing equations and positivity condition. In this paper we propose and verify a novel algebraic property of the crossing equations which provides strong restriction for this program. We show for various types of symmetries $\mathcal{G}$, the crossing equations can be linearly converted into the $SO(N)$ vector crossing equations associated with the $SO(N)\to \mathcal{G}$ branching rules and the transformations satisfy positivity condition. The dynamics constrained by the $\mathcal{G}$-symmetric crossing equations combined with the positivity condition degenerates to the $SO(N)$ symmetric cases, while the non-$SO(N)$ symmetric theories are not directly solvable without introducing the $SO(N)$ symmetry breaking assumptions on the spectrum.

Recently, a novel numerical computation on quantum mechanics by using a bootstrap method was proposed by Han, Hartnoll, and Kruthoff. We consider whether this method works in systems with a $\theta$-term, where the standard Monte-Carlo computation may fail due to the sign problem. As a starting point, we study quantum mechanics of a charged particle on a circle in which a constant gauge potential is a counterpart of a $\theta$-term. We find that it is hard to determine physical quantities as functions of $\theta$ such as $E(\theta )$, except at $\theta =0$ and $\pi$. On the other hand, the correlations among observables for energy eigenstates are correctly reproduced for any $\theta$. Our results suggest that the bootstrap method may work not perfectly but sufficiently well, even if a $\theta$-term exists in the system.

The Casimir effect realizes the existence of static negative energy densities in quantum field theory. We establish physically reasonable conditions for the non-negativity of the total mass of a Casimir apparatus held in equilibrium in the Minkowski background, irrespective of any condensed matter consideration. Specifically, the dynamical equilibrium requires the presence of additional matter to hold the system apart. As long as this extra matter satisfies the dominant energy condition, the mass of the combined system is positive. Thus, the very same reason why energy cannot travel backward in time could be the underlying mechanism behind the positivity of the mass. We discuss the takeaways from the Casimir setting to more general circumstances.

The quantum effective action yields equations of motion and correlation functions including all quantum corrections. We discuss here how it encodes also Noether currents at the full quantum level. Interestingly, the construction can be generalized beyond the standard symmetry transformations that leave the action invariant. We also discuss an extended set of transformations, which change the action by a term that is locally known on the level of the quantum effective action. Associated to such extended gauge transformations are currents for which we obtain a divergence-type equation of motion, but they are not conserved. We call them nonconserved Noether currents. We discuss, in particular, symmetries and extended transformations associated to space-time geometry for relativistic quantum field theories. These encompass local dilatations or Weyl gauge transformation, local Lorentz transformations, and local shear transformations. Together they constitute the symmetry group of the frame bundle $\mathrm{GL}(d)$. The corresponding nonconserved Noether currents are the dilatation or Weyl current, the spin current, and the shear current. In particular, for the latter, we obtain a new divergence-type equation of motion.

In this work, we use a parametrized theory-agnostic approach that connects the observation of black hole quasinormal modes with the underlying perturbation equations, with the goal of reconstructing the potential and the coupling functions appearing in the latter. The fundamental quasinormal mode frequency and its first two overtones are modeled through a second order expansion in the deviations from general relativity, which are assumed to be small but otherwise generic. By using a principal component analysis, we demonstrate that percent-level measurements of the fundamental mode and its overtones can be used to constrain the effective potential of tensor perturbations and the coupling functions between tensor modes and ones of different helicity, without assuming an underlying theory. We also apply our theory-agnostic reconstruction framework to analyze simulated quasinormal mode data produced within specific theories extending general relativity, such as Chern-Simons gravity.

We study the gravito-electromagnetic perturbations of the Kerr-Newman (KN) black hole and identify the two—photon sphere and near-horizon—families of quasinormal modes (QNMs) of the black hole, computing the frequency spectra (for all the KN parameter space) of the modes with the slowest decay rate. We uncover a novel phenomenon for QNMs that is unique to the KN system, namely eigenvalue repulsion between QNM families. Such a feature is common in solid state physics where e.g., it is responsible for energy bands/gaps in the spectra of electrons moving in certain Schrödinger potentials. Exploiting the enhanced symmetries of the near-horizon limit of the near-extremal KN geometry, we also develop a matched asymptotic expansion that allows us to solve the perturbation problem using separation of variables and provides an excellent approximation to the KN QNM spectra near extremality. The KN QNM spectra derived here are needed not only to account for gravitational emission in astrophysical environments, such as the ones probed by LIGO, Virgo and LISA, but also to allow one to extract observational implications of several new physics scenarios, such as minicharged dark-matter or certain modified theories of gravity, whose observables degenerate to those of the KN solution at the scale of binary mergers.

In this work we analyze a solution that mimics the Bardeen solution with a cosmological constant surrounded by quintessence. We show that this solution can be obtained by Einstein equations coupled with nonlinear electrodynamics. We also show that the solution is not always regular and what the conditions for regularity are. We analyze the thermodynamics associated with this type of solution by establishing the form of the Smarr formula and the first law of thermodynamics. We obtain some thermodynamic quantities such as pressure, temperature, heat capacity, and isothermal compressibility. Once we have these thermodynamic quantities, we check if this solution has phase transitions and how it behaves at the points where the transitions occur. For some values of the parameters, we find that the solution exhibits a first-order phase transition, like a van der Waals fluid.

We present a new approach to constrained classical fields that enables the action formalism to dictate how external sources must enter the resulting equations of motion. If symmetries asserted upon the varied fields can be modeled as restrictions in Fourier space, then we prove that these restrictions are automatically applied to external sources in an unambiguous way. In contrast, the typical procedure inserts symmetric Ansätze into the Euler-Lagrange differential equations, even for external sources not being solved. This requires ad hoc constraint of external sources, which can introduce leading-order errors to model systems despite superficial consistency between model field and source terms. To demonstrate, we consider Robertson-Walker cosmologies within general relativity and prove that the influence of pointlike relativistic pressure sources on cosmological dynamics cannot be excluded by theoretical arguments.

Accretion disks surrounding compact objects, and other environmental factors, deviate satellites from geodetic motion. Unfortunately, setting up the equations of motion for such relativistic trajectories is not as simple as in Newtonian mechanics. The principle of general (or Lorentz) covariance and the mass-shell constraint make it difficult to parametrize physically adequate 4-forces. Here, we propose a solution to this old problem. We apply our framework to several conservative and dissipative forces. In particular, we propose covariant formulations for Hooke’s law and the constant force and compute the drag due to gravitational and hard-sphere collisions in dust, gas, and radiation media. We recover and covariantly extend known forces such as Epstein drag, Chandrasekhar’s dynamical friction, and Poynting-Robertson drag. Variable-mass effects are also considered, namely, Hoyle-Lyttleton accretion and the variable-mass rocket. We conclude with two applications: (1) The free-falling spring, where we find that Hooke’s law corrects the deviation equation by an effective anti–de Sitter tidal force and (2) black hole infall with drag. We numerically compute some trajectories on a Schwarzschild background supporting a dustlike accretion disk.

We study a model of two-field ultraslow-roll (USR) inflation bounded by a curve in the field space. Curvature perturbations and non-Gaussianities can be enhanced both during the USR phase and from the inhomogeneities at the boundary. We employ the full nonlinear $\delta N$ formalism to calculate the probability distribution function (PDF) for curvature perturbation nonperturbatively and show that nonlinear effects can significantly enhance the abundance of primordial black holes (PBHs). For large curvature perturbations, the PDF has a universal exponential tail, but for the intermediate values, the PDF—and, therefore, the abundance of the PBHs—depend sensitively on the geometry of the boundary.