In this work, a modified Nambu-Jona-Lasinio (NJL) model with proper-time regularization is employed to study the properties of hypothetical nonstrange quark stars. The coupling constant of the four-fermion interaction in the conventional NJL model is modified as $G=G_1+G_2⟨\overline{\psi }\psi ⟩$ to highlight the feedback of the quark propagator to the gluon propagator. To study the dependence of the equation of state (EOS) on this modification as well as the vacuum pressure, we choose nine representative EOSs for comparison. It is found that a smaller $G_1$ leads to a stiffer EOS, and a higher vacuum pressure (i.e., a smaller bag constant) yields a softer EOS at low energy density. It is further shown that the heaviest quark star under this modified NJL model satisfies not only the recent mass measurement of PSR $\mathrm{J}0740+6620$, but also the radius constraints from x-ray timing observations. The corresponding tidal deformability is also in agreement with the observations of GW170817.

Recently, bootstrap methods from conformal field theory have been adapted for studying the energy spectrum of various quantum mechanical systems. In this paper, we consider the application of these methods in obtaining the spectrum from the Schrödinger equation with periodic potentials, paying particular attention to the Kronig-Penney model of a particle in a one-dimensional lattice. With an appropriate choice of operator basis involving position and momenta, we find that the bootstrap approach efficiently computes the band gaps of the energy spectrum but has trouble effectively constraining the minimum energy. We show how applying more complex constraints involving higher powers of momenta can potentially remedy such a problem. We also propose an approach for analytically constructing the dispersion relation associated with the Bloch momentum of the system.

Real-time quantum simulation of quantum field theory in $(3+1)\mathrm{D}$ requires large quantum computing resources. With a few-qubit quantum computer, we develop a novel algorithm and experimentally study the Schwinger effect, the electron-positron pair production in a strong electric field, in $(3+1)\mathrm{D}$. The resource reduction is achieved by treating the electric field as a background field, working in Fourier space transverse to the electric field direction, and considering parity symmetry, such that we successfully map the three spatial dimension problems into one spatial dimension problems. We observe that the rate of pair production of electrons and positrons is consistent with the theoretical predication of the Schwinger effect. Our work paves the way towards exploring quantum simulation of quantum field theory beyond one spatial dimension.

For the purpose of minimizing the number of sample model evaluations, we propose and study algorithms that utilize (sequential) versions of likelihood-to-evidence ratio neural estimation. We apply our algorithms to a supersymmetric interpretation of the anomalous muon magnetic dipole moment in the context of a phenomenological minimal supersymmetric extension of the standard model, and recover nontrivial models in an experimentally constrained theory space. Finally we summarize further potential possible uses of these algorithms in future studies.

Nuclear scattering events with large momentum transfer in atomic, molecular, or solid-state systems may result in electronic excitations. In the context of atomic scattering by dark matter (DM), this is known as the Migdal effect, but the same effect has also been studied in molecules in the chemistry and neutron scattering literature. Here we present two distinct Migdal-like effects from DM scattering in molecules, which we collectively refer to as the molecular Migdal effect: a center-of-mass recoil, equivalent to the standard Migdal treatment; and a nonadiabatic coupling resulting from corrections to the Born-Oppenheimer approximation. The molecular bonds break spherical symmetry, leading to large daily modulation in the Migdal rate from anisotropies in the matrix elements. Our treatment reduces to the standard Migdal effect in atomic systems but does not rely on the impulse approximation or any semiclassical treatments of nuclear motion and as such may be extended to models where DM scatters through a long-range force. We demonstrate all of these features in a few simple toy models of diatomic molecules, namely, ${\mathrm{H}}_2^{+}$, ${\mathrm{N}}_2$, and CO, and find total molecular Migdal rates competitive with those in semiconductors for the same target mass. We discuss how our results may be extended to more realistic targets comprised of larger molecules which could be deployed at the kilogram scale.

We have recently studied hidden-charm pentaquarks, $c\overline{c}qqq$, using the dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A pattern was obtained that compares well with the experimental data. We extend our description to other flavor sectors which can be framed within the same type of structures discussed in the original paper. A detailed comparison is made with other results in the literature and with experimental data. The predictions will be a useful tool to discriminate between different models of multiquark system dynamics.

The molecular nature of $D_{s0}^{*}(2317)$ and $D_{s1}(2460)$ have been extensively studied from the perspective of their masses, decay properties, and production rates. In this work, we study the weak decays of $B\to {\overline{D}}^{(*)}{D}_{s0}^{*}(2317)$ and $B\to {\overline{D}}^{(*)}{D}_{s1}(2460)$ by invoking triangle diagrams where the $B$ meson first decays weakly into ${\overline{D}}^{(*)}{D}_s^{(*)}$ and $J/\psi K({\eta }_{c}K$), and then the $D_{s0}^{*}(2317)$ and $D_{s1}(2460)$ are dynamically generated by the final-state interactions of $D_s^{(*)}\eta$ and $D^{(*)}K$ via exchanges of $\eta$ and $D^{(*)}$ mesons. The obtained absolute branching fractions of $\mathrm{Br}[B\to {\overline{D}}^{(*)}{D}_{s0}^{*}(2317)]$ are in reasonable agreement with the experimental data, while the branching fractions of $\mathrm{Br}[B\to {\overline{D}}^{(*)}{D}_{s1}(2460)]$ are smaller than the experimental central values by almost a factor of two to three. We tentatively attribute such a discrepancy to either reaction mechanisms missing in the present work or the likely existence of a relatively larger $c\overline{s}$ component in the $D_{s1}(2460)$ wave function.

The decay amplitude analyses of $B^{\pm }\to {\pi }^{+}{\pi }^{-}{\pi }^{\pm }$ decays in the Dalitz plot performed by LHCb indicate that $CP$ asymmetry for the dominant quasi-two-body decay $B^{\pm }\to \rho (770{)}^0{\pi }^{\pm }$ was found to be consistent with zero in all three approaches for the $S$-wave component and that $CP$-violation effects related to the interference between the $\rho (770{)}^0$ resonance and the $S$-wave were clearly observed. We show that the nearly vanishing $CP$ violation in $B^{\pm }\to {\rho }^0{\pi }^{\pm }$ is understandable within the framework of QCD factorization. There are two $1/m_b$ power corrections, one from penguin annihilation and the other from hard spectator interactions. They contribute destructively to ${\mathcal{A}}_{CP}(B^{\pm }\to {\rho }^0{\pi }^{\pm })$ to render it compatible with zero, in contrast to the sizable negative $CP$ asymmetry predicted in most of the existing models. We next show that the measured interference pattern between the $\rho$ and $S$-wave contributions in the low $m_{{\pi }^{+}{\pi }^{-}}$ region separated by the sign of value of $\cos \theta$ with $\theta$ being the angle between the two same charged pions measured in the rest frame of the $\rho$ resonance can be explained in terms of the smallness of ${\mathcal{A}}_{CP}(B^{+}\to {\rho }^0{\pi }^{+})$ and the interference between $\rho (770)$ and $\sigma /f_0(500)$. If $CP$ asymmetry in $B^{\pm }\to {\rho }^0{\pi }^{\pm }$ is not negligible as predicted in many existing models, the observed interference pattern will be destroyed. We conclude that the experimental observation of the interference pattern between $P$- and $S$-waves in the low-$m_{{\pi }^{+}{\pi }^{-}}$ region between 0.5 and 1.0 GeV is consistent with a nearly vanishing $CP$ violation in $B^{\pm }\to {\rho }^0{\pi }^{\pm }$.

Finite temperature effects in the Standard Model tend to restore the electroweak symmetry in the early universe, but new fields coupled to the Higgs field may as well reverse this tendency, leading to the so-called electroweak symmetry nonrestoration (EW SNR) scenario. Previous works on EW SNR often assume that the reversal is due to the thermal fluctuations of new fields with negative quartic couplings to the Higgs, and they tend to find that a large number of new fields are required. We observe that EW SNR can be minimally realized if the field(s) coupled to the Higgs field develop(s) a stable condensate. We show that one complex scalar field with a sufficiently large global-charge asymmetry can develop a condensate as an outcome of thermalization and keep the electroweak symmetry broken up to temperatures well above the electroweak scale. In addition to providing a minimal benchmark model, our work hints on a class of models involving scalar condensates that yield electroweak symmetry nonrestoration in the early universe.

Locating the critical endpoint of QCD and the region of a first-order phase transition at finite baryon chemical potential is an active research area for QCD matter. We provide a gravitational dual description of QCD matter at finite baryon chemical potential ${\mu }_B$ and finite temperature using the nonperturbative approach from gauge/gravity duality. After fixing all model parameters using state-of-the-art lattice QCD data at zero chemical potential, the predicted equations of state and QCD trace anomaly relation are in quantitative agreement with the latest lattice results. We then give the exact location of the critical endpoint as well as the first-order transition line, which is within the coverage of many upcoming experimental measurements. Moreover, using the data from our model at finite ${\mu }_B$, we calculate the spectrum of the stochastic gravitational wave background associated with the first-order QCD transition in the early Universe, which could be observable via pulsar timing in the future.

The LHCb Collaboration has recently discovered a structure around 6.9 GeV in the double-$J/\psi$ mass distribution, possibly a first fully charmed tetraquark state $X(6900)$. Based on vector-meson dominance (VMD) such a state should have a significant branching ratio for decaying into two photons. We show that the recorded LHC data for the light-by-light scattering may indeed accommodate for such a state, with a $\gamma \gamma$ branching ratio of order of ${10}^{-4}$, which is larger even than the value inferred by the VMD. The spin-parity assignment $0^{-+}$ is in better agreement with the VMD prediction than $0^{++}$, albeit not significantly at the current precision. Further light-by-light scattering data in this region, clarifying the nature of this state, should be obtained in the Run 3 and probably in the high-luminosity phase of the LHC (Run 4 etc.).

We exploit an ambiguity somewhat hidden in Noether’s theorem to derive systematically, for relativistic field theories, the stress-energy tensor’s improvement terms that are associated with additional spacetime symmetries beyond translations. We work out explicitly the cases of Lorentz invariance, scale invariance, and full conformal invariance. The main idea is to use, directly in the translation Noether theorem, the fact that these additional symmetries can be thought of as suitably modulated translations. Compared to more standard derivations of the improvement terms, ours (1) unifies all different cases in a single framework, (2) involves no guesswork, (3) yields the desired algebraic properties (symmetry and/or tracelessness) of the stress-energy tensor off-shell, and (4) unifies the translation Noether theorem with those of the additional spacetime symmetries, yielding at the same time both the improved stress-energy tensor and the additional Noether currents.

We investigate the low-temperature behavior of a system in a spontaneously broken symmetry phase described by a Euclidean quantum $\lambda {\phi }_{d+1}^4$ model with quenched disorder. We study the effects of the disorder linearly coupled to the scalar field using a series representation for the averaged generating functional of connected correlation functions in terms of the moments of the partition function. To deal with the strongly correlated disorder in imaginary time, we employ the equivalence between the model defined in a $d$-dimensional space with imaginary time with the statistical field theory model defined on a space ${\mathbb{R}}^d\times S^1$ with anisotropic quenched disorder. Next, using stochastic differential equations and fractional derivatives, we obtain the Fourier transform of the correlation functions of the disordered system at tree level. In one-loop approximation, we prove that there is a denumerable collection of moments of the partition function that can develop critical behavior. Our main result is that, even with the bulk in the ordered phase, there are many critical compactified lengths that take each of the moments of the partition function from an ordered to a disordered phase. This is a sign of generic scale invariance emergence in the system.

Lorentz violation modifies the dispersion relation of gravitational waves (GWs), and induces birefringence and anisotropy in propagation. Our study shows that Lorentz violation can also activate multiple polarizations of GWs. We use the gauge invariants to investigate the polarizations of GWs in the bumblebee gravity model, and obtain the following results. (i) For a vector background $b^{\mu }$ with only a nonzero temporal component $b^t$, there are five independent propagating degrees of freedom (d.o.f.), which is similar to the Einstein-æther theory. (ii) The presence of a spatial component in the background defines a preferred spatial direction which breaks rotational symmetry. We denote $\widehat{\mathit{b}}$ as the direction of the spatial part of the background and $b_s$ as its length. If GWs propagate along $\widehat{\mathit{b}}$, the polarization content is similar to the purely timelike case. (iii) If the propagation direction of GWs is separated by an angle $\beta$ to $\widehat{\mathit{b}}$, and $\beta =\arccos (b^t/b_s)$, there are only two tensor polarizations. (iv) If $\beta \ne \arccos (b^t/b_s)$, there are only two independent d.o.f., and the vector and scalar modes degenerate with the tensor modes. The tensor perturbations can activate a mixture of all six polarizations simultaneously. Finally, we point out the difference in GWs between the bumblebee gravity model and the minimal Standard-Model Extension framework in the linearized regime. Current observations have placed stringent constraints on the anisotropy induced by the background, while our theoretical study still reveals some novel phenomena and provides more understanding about the interaction between the Lorentz-violating vector field and gravity.

A near-future detection of the 21-cm signal from the epoch of reionization will provide unique opportunities to probe the underlying cosmology, provided that such cosmological information can be extracted with precision. To this end, we further develop effective field theory (EFT) inspired techniques for the 21-cm brightness temperature field during the epoch of reionization, incorporating renormalized bias and a treatment of redshift space distortions. Notably, we confirm that in redshift space, measures of the 21-cm brightness, e.g., the power spectrum, should have irreducible contributions that lack a bias coefficient and therefore contain direct, astrophysics-free information about the cosmological density field; in this work, we study this effect beyond linear order. To validate our theoretical treatment, we fit the predicted EFT Fourier-space shapes to the thesan suite of hydrodynamical simulations of reionization at the field level, where the considerable number of modes prevents overfitting. We find agreement at the level of a few percent between the 21-cm power spectrum from the EFT fits and simulations over the wave number range $k\lesssim 0.8\mathrm{h}/\mathrm{Mpc}$ and neutral fraction $x_{\mathrm{HI}}\gtrsim 0.4$, which is imminently measurable by the Hydrogen Epoch of Reionization Array and future experiments. The ability of the EFT to describe the 21-cm signal extends to simulations that have different astrophysical prescriptions for reionization as well as simulations with interacting dark matter.

Following up large numbers of candidates in continuous gravitational-wave searches presents a challenge, particularly in regard to computational power and the time required to manually scrutinize each of the candidates. It is important to design and test good follow-up procedures that are safe (i.e., minimize false dismissals) and computationally efficient across many search configurations. We investigate two follow-up procedures, or “vetoes,” both of which exploit the Doppler modulation predicted in astrophysical signals. In particular, we introduce the concept of using an effective point spread function as part of our veto criteria. We take advantage of a well-established semicoherent search algorithm based on a hidden Markov model to study various search configurations and to generalize the veto criteria by considering the overall veto performance in terms of efficiency and safety. The results can serve as a guideline for follow-up studies in future continuous gravitational-wave searches using a hidden Markov model algorithm. The results also apply qualitatively to other semicoherent search algorithms.

We study the collective modes of gluons in an anisotropic thermal medium in the presence of a constant background magnetic field using the hard-thermal-loop perturbation theory. The momentum space anisotropy of the medium has been incorporated through the generalized Romatschke-Strickland form of the distribution function, whereas the magnetic modification arising from the quark loop contribution has been taken into account in the lowest Landau level approximation. We consider two special cases: (i) a spheroidal anisotropy with the anisotropy vector orthogonal to the external magnetic field and (ii) an ellipsoidal anisotropy with two mutually orthogonal vectors describing anisotropies along and orthogonal to the field direction. The general structure of the polarization tensor in both cases is equivalent and consists of six independent basis tensors. We find that the introduction of momentum anisotropy ingrains azimuthal angular dependence in the thermomagnetic collective modes. Our study suggests that the presence of a strong background magnetic field can significantly reduce the growth rate of the unstable modes, which may have important implications in the equilibration of magnetized quark-gluon plasma.

We study the collision of two optical laser pulses in a pump-probe setup using beams with circular and elliptic cross section and estimate the number of discernible signal photons induced by quantum vacuum nonlinearities. In this analysis we study strategies to optimize the quantum vacuum signal discernible from the background of the driving lasers. One of the main results is that the collision of two maximally focused lasers does not lead to the best discernible signal. Instead, widening the focus typically improves the signal to background separation in the far field. For petawatt class lasers, an optimal choice of the focus waist yields several discernible photons per shot in contrast to no discernible signal for tight focusing. Further enhancement is possible by using an elliptical waist.

We present a unified model that solves four major problems of the standard model, i.e., neutrino masses, origin of matter, the strong $CP$ problem and dark matter using the framework of the Affleck-Dine (AD) mechanism. The AD field is responsible for inflation, origin of matter, and neutrino masses which arise at the one loop level. Neutrino masses are therefore intimately connected to the baryon-to-photon ratio of the Universe. The dark matter in the model is the axion field used to solve the strong $CP$ problem. The model has a near massless Majorana fermion which contributes to $\mathrm{\Delta }{N}_{\mathrm{eff}}\sim 0.1$ in the early Universe that can be tested in the upcoming CMB-S4 experiment.

One of the major open problems of neutrino physics is mass ordering (MO). We discuss the prospects of measuring MO with two under-construction experiments T2HK and JUNO. JUNO alone is expected to measure MO with greater than $3\sigma$ significance as long as certain experimental challenges are met. In particular, JUNO needs better than 3% energy resolution for MO measurement. On the other hand, T2HK has rather poor prospects at measuring the MO, especially for certain ranges of the $CP$ violating parameter ${\delta }_{CP}$, posing a major drawback for T2HK. In this article we show that the synergy between JUNO and T2HK will bring twofold advantage. First, the synergy between the two experiments helps us determine the MO at a very high significance. With the baseline setup of the two experiments, we have a greater than $9\sigma$ determination of the MO for all values of ${\delta }_{CP}$. Second, the synergy also allows us to relax the constraints on the two experiments. We show that JUNO could perform extremely well even for an energy resolution of 5%, while for T2HK the MO problem with “bad” values of ${\delta }_{CP}$ goes away. The MO sensitivity for the combined analysis is expected to be greater than $6\sigma$ for all values of ${\delta }_{CP}$ and with just 5% energy resolution for JUNO.