Sydney Coleman’s Q-ball remains a compelling instance of the formation of localized objects within classical field theory, independently of the quantum evolution. The theoretical possibility of such objects forming and colliding in the early Universe from models such as Affleck-Dine fragmentation, or from a number of mechanisms where they are produced copiously with various sizes and charges to constitute dark matter in the Universe, makes it important to study in detail Q-ball collision phenomenology. In this work, we present certain results from the study of Q-ball collisions and their generation of gravitational waves, using a new general code package for scalar fields coupled to gravity. We then comment on the possibility of future gravitational wave detectors searching for signals of Q-ball collisions.

Kelvin probe force microscopy (KPFM) is widely used to measure the surface potential on samples, from which the electrostatic patch force can be calculated. However, since the KPFM measurements represent a weighted average of local potentials on the sample, the accuracy of the evaluation critically depends on the precision and lateral resolution of the method. In this paper, we investigate the influence of this averaging effect on patch force estimations using both analytic and numerical methods. First, we derive the correlation functions of patch potential and establish the formulas for calculating the electrostatic patch forces in the parallel-plate geometry, with and without consideration of the KPFM measurement effect. Thus, an analytic method is established to determine the accuracy of patch force evaluation when the statistical parameters of the patch potential and the lateral resolution of the KPFM are given. Second, numerical simulations are employed to explore the dependence of estimated patch forces on the lateral resolution of KPFM under more realistic conditions. Both analytic and numerical results show a similar dependence of the patch force estimation on the patch characteristic size, potential fluctuation, and the lateral resolution of KPFM. It is also found that the underestimation of the patch force becomes less sensitive to the resolution of KPFM as the separation between plates increases. The results of this study could provide useful guidance for the accurate evaluation of electrostatic patch forces using KPFM.

Using lattice QCD simulations with $\mathcal{O}(a)$-improved Wilson quarks and physical up, down, and strange quark masses, we investigate the properties of thermal QCD matter at the temperatures $T=\{128,154,192\}\mathrm{MeV}$ with a fixed lattice spacing $a=0.064\mathrm{fm}$ and volume $V=(6.1\mathrm{fm}{)}^3$. We find that the pion quasiparticle, defined as the low-energy pole in the two-point function of the axial charge, becomes lighter as the temperature increases, and we give an argument based on hydrodynamics as to why the pole becomes purely diffusive above the chiral crossover. We study the thermal modification of the isovector vector spectral function using the Backus-Gilbert method, finding an enhancement at low energies and a depletion at energies around 1 GeV. The analogous study of the axial-vector channel reveals a larger enhancement at energies below 1 GeV, and we show that these findings are consistent with rigorous spectral sum rules. The difference between vector and axial-vector correlators, an order parameter for chiral symmetry, turns out to be overall suppressed by more than an order of magnitude at the crossover.

We investigate heavy-light quark systems within the framework of the QCD instanton vacuum, focusing on the $N_f=1$ light flavor case. We derive an effective heavy-light quark interaction from the low-energy QCD partition function and construct a heavy-meson effective Lagrangian. The physical residual mass of heavy mesons, $\mathrm{\Lambda }$, is determined by employing compositeness and normalization conditions. We calculate the masses of $D$ and $B$ mesons and their weak decay constants to the leading order and next-to-leading order in the $1/m_Q$ expansion. The current results for $f_D$ and $f_B$ are in good agreement with recent lattice QCD data and Particle Data Group (PDG) average values.

The strong longitudinal expansion characteristic of heavy-ion collisions leads to universal attractor behavior of the resulting drop of quark-gluon plasma (QGP) already at very early times. Assuming approximate boost invariance and neglecting transverse expansion at the initial time, we incorporate subsequent transverse dynamics of this system by linearizing the Mueller-Israel-Stewart theory around the transversely homogeneous attractor. The result is a system of coupled ordinary differential equations which describes the proper-time evolution of Fourier modes encoding the transverse structure of the initial energy deposition. The late-time asymptotic behavior of these solutions is described by transseries which make manifest the stability of the attractor against transverse perturbations. In this framework, information about the structure of the plasma in the transverse plane resides mostly in exponentially suppressed corrections to evolution along the attractor, which are not yet negligible at freeze-out. These findings also suggest a simple numerical approach to QGP dynamics using a finite number of Fourier modes. Physical observables can be expressed in terms of the asymptotic data evaluated at freeze-out. We demonstrate the efficacy of this approach by calculating the final multiplicity distributions and collective flow coefficients.

Recent experimental progress on baryonic rare decays has spurred a deeper investigation on flavor-changing neutral current transitions in the baryon sector. Within the framework of QCD sum rules, we derive a complete set of form factors for the ${\mathrm{\Lambda }}_c\to p$ process in the large recoil region and use the $z$-series parametrization to extrapolate them across the full physical range. Employing these form factors and flavor symmetries, we compute branching fractions for the decays ${\mathrm{\Lambda }}_c\to p{e}^{+}{e}^{-}$ and ${\mathrm{\Lambda }}_c\to p{\mu }^{+}{\mu }^{-}$, as well as for rare ${\mathrm{\Xi }}_c$ decay modes. We examine as well the new physics effects through specific angular observables such as the lepton forward-backward asymmetry and the fraction of longitudinally polarized dileptons. Results indicate that new physics models may be testified in baryonic rare decays, with immense data collected in running and future colliders.

In a large class of chiral gauge theories in four dimensions it was found that certain natural assumption about the bifermion condensates leads to the infrared effective theory where the ’t Hooft anomaly matching conditions are satisfied in an entirely evident fashion, without need of verifying arithmetic equations. This is due to the fact that in these systems, characterized by dynamical color (and flavor) symmetry breaking, the quantum numbers and multiplicities of the low-energy massless fermions match exactly those of the fermions in the UV theory which do not condense and remain massless, with respect to the unbroken symmetries. This means also that the stronger constraints following from the matching request of mixed anomalies involving certain generalized 1-form center symmetries, as well as some global anomalies such as Witten’s $SU(2)$ anomaly, are all fully satisfied. It is the aim of this note to clarify better the working of this phenomenon (which we call natural anomaly matching), correct some earlier statements made about it, and illustrate it further with a few new examples.

We investigate the $W$ boson’s exotic decay channel, $W\to \ell \ell \ell \nu$, at the LHC. Although the four-body final states suppress the decay branching ratio, the large production of $W$ bosons makes detecting and precisely measuring this decay probability entirely feasible. Our simulation study indicates that this tiny branching ratio can be measured with subpercent precision at the HL-LHC. This decay channel can also constrain Standard Model extensions. Using the $L_{\mu }-L_{\tau }$ model as a benchmark, we find that the current bound on the gauge coupling for $Z^{\prime }$ mass in the range of [4, 75] GeV can significantly improve.

We report the first amplitude analyses of the decays $D^0\to {\pi }^{+}{\pi }^{-}\eta$ and $D^{+}\to {\pi }^{+}{\pi }^0\eta$ using a data sample taken with the BESIII detector at the center-of-mass energy of 3773 MeV, corresponding to an integrated luminosity of $7.9{\mathrm{fb}}^{-1}$. The contribution from the process $D^{0(+)}\to a_0(980{)}^{+}{\pi }^{-(0)}$ is significantly larger than the $D^{0(+)}\to a_0(980{)}^{-(0)}{\pi }^{+}$ contribution. The ratios $\mathcal{B}(D^0\to a_0(980{)}^{+}{\pi }^{-})/\mathcal{B}(D^0\to a_0(980{)}^{-}{\pi }^{+})$ and $\mathcal{B}(D^{+}\to a_0(980{)}^{+}{\pi }^0)/\mathcal{B}(D^{+}\to a_0(980{)}^0{\pi }^{+})$ are measured to be ${7.5}_{-0.8\mathrm{stat}}^{+2.5}\pm {1.7}_{\mathrm{syst}}$ and $2.6\pm {0.6}_{\mathrm{stat}}\pm {0.3}_{\mathrm{syst}}$, respectively. The measured $D^0$ ratio disagrees with the theoretical predictions by orders of magnitudes, thus implying a substantial contribution from final-state interactions.

We construct a soliton train configuration with holographic superfluid model under anti–de Seitter (AdS) soliton background. We investigate the stability of a soliton train using Bloch waves under two distinct quantization schemes. Upon imposing a minor perturbation on the soliton train system, it has been observed that there exist two elastic modes and one phonon mode. Most importantly, we find, under soliton train background, that there is a rich phase diagram concerning the chemical potential under standard quantization. Nevertheless, there are no unstable modes under alternative quantization.

In this paper, we study tree-level four-point scattering amplitudes and present a novel approach to partial-wave unitarity that bypasses a lot of technical difficulties of previous approaches. In passing, we explicitly demonstrate that our approach provides a very suggestive form for the partial-wave coefficients in a natural way which is our main result. We use the Coon amplitude to exemplify this method and show how it makes important properties such as partial-wave unitarity manifest. A secondary by-product of our analysis is simple form for the partial-wave coefficients of the Coon amplitude as a single sum.

Information geometry provides differential geometric concepts like a Riemannian metric, connections and covariant derivatives on spaces of probability distributions. We discuss here how these concepts extend in a functional sense to quantum field theories in the Euclidean domain which can also be seen as statistical field theories. The geometry has a dual affine structure corresponding to source fields or expectation value fields seen as coordinates. In the latter version the coordinates label the macrostates of the classical field theory. A key concept is a new generating functional, which is a functional generalization of the Kullback-Leibler divergence. From its functional derivatives one can obtain connected as well as one-particle irreducible correlation functions. It also encodes directly the geometric structure, i.e. the functional Fisher information metric and the two dual connections, and it determines asymptotic probabilities for field configurations through Sanov’s theorem. Based on the two dual connections one can construct covariant functional derivatives which allow one to calculate connected and one-particle irreducible correlation functions in general functional coordinate systems.

The structure of the normal modes of vibration of rotationally invariant $n$-vortices in the Ginzburg-Landau/Abelian Higgs model is completely unveiled for any value of the coupling constant.

We study the propagation of a domain wall (kink) of the ${\varphi }^4$ model in a radially symmetric environment defined by a gravity source. This source introduces a Schwarzschild-like geometry. We introduce an effective model that accurately describes the dynamics of the kink center. This description works well even outside the perturbation region, i.e., even for large masses of the gravitating object. We observed that such a spherical domain wall surrounding a star-type object inevitably “collapses,” i.e., shrinks in radius toward the origin and offer an understanding of the latter phenomenology. The relevant analysis is presented for a circular domain wall and a spherical one.

The detailed structure of the peaks appearing in the density-density correlation function for an acoustic black hole formed by a Bose-Einstein condensate is analytically discussed for a particular, but physically meaningful, sound velocity profile that allows the field modes to be exactly computed.

Pair creation is a fundamental prediction of quantum field theory in curved spacetimes. While classical aspects of this phenomenon have been observed, the experimental confirmation of its quantum origin remains elusive. In this article, we quantify the entanglement produced by pair creation in two dimensional Bose-Einstein condensate (BEC) analogs of expanding universes and examine the impact of various experimental factors, including decoherence from thermal noise and losses. Our analysis evaluates the feasibility of detecting entanglement in these systems and identifies optimal experimental configurations for achieving this goal. Focusing on the experimental setup detailed in Viermann et al. [Quantum field simulator for dynamics in curved spacetime, Nature (London) 611, 260 (2022)], we demonstrate that entanglement can be observed in these BEC analogs at a significance level of $\sim 2\sigma$ with current capabilities, and at $\gtrsim 3.3\sigma$ with modest improvements. Achieving this would provide unequivocal evidence of the quantum nature of pair creation and validate one of the most iconic predictions of quantum field theory in curved spacetimes.

Binary neutron star mergers produce massive, hot, rapidly differentially rotating neutron star remnants; electromagnetic and gravitational wave signals associated with the subsequent evolution depend on the stability of these remnants. Stability of relativistic stars has previously been studied for uniform rotation and for a class of differential rotation with monotonic angular velocity profiles. Stability of those equilibria to axisymmetric perturbations was found to respect a turning point criterion: along a constant angular momentum sequence, the onset of unstable stars is found at maximum density less than but close to the density of maximum mass. In this paper, we test this turning point criterion for nonmonotonic angular velocity profiles and nonisentropic entropy profiles, both chosen to more realistically model postmerger equilibria. Stability is assessed by evolving perturbed equilibria in 2D using the spectral einstein Code. We present tests of the code’s new capability for axisymmetric metric evolution. We confirm the turning point theorem and determine the region of our rotation law parameter space that provides highest maximum mass for a given angular momentum.

Astrophysical population simulations predict that a subset of dynamically formed binary black holes (BBHs) may possess eccentricity $\gtrsim 0.1$ at a gravitational wave (GW) frequency of 10 Hz. Presently, the LIGO-Virgo-KAGRA (LVK) Collaboration tests general relativity (GR) assuming that the binary eccentricity has decayed well before it enters the detector’s frequency band. The detection of an eccentric binary could allow us to test GR in a regime inaccessible with binaries in circular orbits. Previous works have also shown that binary eccentricity can bias GR tests if unaccounted for. Here we develop two methods to extend parametrized tests of GR to eccentric binaries. The first method extends the standard null parametrized test for quasicircular binaries by adding fractional deviations at each post-Newtonian (PN) order in the eccentric part of the GW phasing (assuming the small-eccentricity limit). Simultaneous measurement of the circular and eccentric deviation parameters ($\delta \widehat{\phi },\delta {\widehat{\phi }}^e$) allows us to constrain deviations from GR for eccentric binaries. While strong constraints on the deviation parameters are not achievable with LIGO’s projected sensitivity, Cosmic Explorer (CE) can constrain 1PN deviations to $|\delta {\widehat{\phi }}_2|\lesssim 2\times {10}^{-2}$ and $|\delta {\widehat{\phi }}_2^e|\lesssim {10}^{-1}$ for spinning BBHs. The multibanding of LISA and CE observations can constrain these deviations to $|\delta {\widehat{\phi }}_2|\lesssim 3\times {10}^{-3}$ and $|\delta {\widehat{\phi }}_2^e|\lesssim 2\times {10}^{-2}$. The second method looks for GR deviations in the rate of periastron advance. We modify the relation between the radial and azimuthal frequencies by modifying the periastron advance per orbit $\mathrm{\Delta }\mathrm{\Phi }\equiv 2\pi k$ via $k\to k(1+\mathrm{\Delta }\alpha )$. We derive a parametrized phase expansion for nonspinning eccentric binaries in terms of a non-GR deviation parameter $\mathrm{\Delta }\alpha$ that captures deviations in the periastron advance relative to the GR prediction ($\mathrm{\Delta }{\alpha }^{\mathrm{GR}}\to 0$). The parameter $\mathrm{\Delta }\alpha$ can be constrained with LIGO to $|\mathrm{\Delta }\alpha |\lesssim 4\times {10}^{-2}$ (with $1\sigma$ confidence). For a typical binary neutron star (BNS) system, $\mathrm{\Delta }\alpha$ can be measured with $|\mathrm{\Delta }\alpha |\lesssim 8\times {10}^{-3}$ in LIGO. With CE sensitivity, the bounds on $\mathrm{\Delta }\alpha$ improve by $\sim 1$ order of magnitude for BBHs and $\sim 2$ orders of magnitude for BNS. Multiband sources observed by LISA and CE provide an improved constraint of $|\mathrm{\Delta }\alpha |\lesssim 3\times {10}^{-5}$. The space-based detector DECIGO provides the best constraint on $\mathrm{\Delta }\alpha$ with $|\mathrm{\Delta }\alpha |\lesssim 8\times {10}^{-6}$.

Classical clocks measure proper time along their worldline, and Riemannian geometry provides tools for predicting the time shown by clocks in both flat and curved spacetimes. Common approaches to time in quantum systems, based for instance on wave functions or density matrices, tend to obscure this geometric property at the quantum level. Here, a new framework is demonstrated for perturbing the classical path-length functional to include quantum degrees of freedom within a modified Riemannian geometry. In this framework, a quantum clock travels on geodesics of a family of spacetimes deformed by parameters specifying the clock’s quantum state. Detailed derivations provide potentially testable corrections to gravitational time-dilation in Schwarzschild spacetime that scale with the ratio of the clock’s Compton wavelength to its wave packet’s spatial extent.