We discuss the consequences of the quantum uncertainty on the spectrum of the electron emitted by the $\beta$-processes of a tritium atom bound to a graphene sheet. We analyze quantitatively the issue recently raised by Cheipesh, Cheianov, and Boyarsky [Phys. Rev. D 104, 116004 (2021)], and discuss the relevant timescales and the degrees of freedom that can contribute to the intrinsic spread in the electron energy. We perform careful calculations of the potential between tritium and graphene with different coverages and geometries. With this at hand, we propose possible avenues to mitigate the effect of the quantum uncertainty.

This paper presents the analysis of the data acquired during the first physics run of the Taiwan Axion Search Experiment with Haloscope (TASEH), a search for axions using a microwave cavity at frequencies between 4.70750 and 4.79815 GHz. The data were collected from October 13, 2021 to November 15, 2021, and are referred to as the CD102 data. The analysis of the TASEH CD102 data excludes models with the axion-two-photon coupling $|g_{a\gamma \gamma }|\gtrsim 8.1\times {10}^{-14}{\mathrm{GeV}}^{-1}$, a factor of 11 above the benchmark Kim-Shifman-Vainshtein-Zakharov model for the mass range $19.4687<m_a<19.8436\mu \mathrm{eV}$.

Searches are performed for nonresonant and resonant di-Higgs boson production in the $b\overline{b}\gamma \gamma$ final state. The dataset used corresponds to an integrated luminosity of $139{\mathrm{fb}}^{-1}$ of proton–proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No excess above the expected background is found and upper limits on the di-Higgs boson production cross sections are set. A 95% confidence-level upper limit of 4.2 times the cross section predicted by the Standard Model is set on $pp\to HH$ nonresonant production, where the expected limit is 5.7 times the Standard Model predicted value. The expected constraints are obtained for a background hypothesis excluding $pp\to HH$ production. The observed (expected) constraints on the Higgs boson trilinear coupling modifier ${\kappa }_{\lambda }$ are determined to be $[-1.5,6.7]$ $([-2.4,7.7])$ at 95% confidence level, where the expected constraints on ${\kappa }_{\lambda }$ are obtained excluding $pp\to HH$ production from the background hypothesis. For resonant production of a new hypothetical scalar particle $X$ ($X\to HH\to b\overline{b}\gamma \gamma$), limits on the cross section for $pp\to X\to HH$ are presented in the narrow-width approximation as a function of $m_X$ in the range $251\mathrm{GeV}\le m_X\le 1000\mathrm{GeV}$. The observed (expected) limits on the cross section for $pp\to X\to HH$ range from 640 fb to 44 fb (391 fb to 46 fb) over the considered mass range.

For the case of two light flavors, we propose the stringy description of the system made of one heavy and one light quark-antiquark pair, with the aim of exploring the two lower-lying Born-Oppenheimer potentials as a function of a separation of the heavy quark-antiquark pair. Our analysis reveals three critical separations related to the processes of string reconnection, breaking and junction annihilation. In particular, for the ground-state potential, only the process of string reconnection matters. We find that a tetraquark state makes the dominant contribution to the potential of the first excited state at small separations, and this is the big difference with the $QQ\overline{q}\overline{q}$-quark system where it does so to the ground state potential. Another big difference is the emergence of the full diquark picture $[Qq][\overline{Q}\overline{q}]$ rather than the partial picture $QQ[\overline{q}\overline{q}]$ for the tetraquark state. On the other hand, the scales of string junction annihilation, below which the systems can be thought of mainly as the compact tetraquarks, are very close for both cases and become almost the same if the phenomenological rule $E_{\mathrm{QQ}}=\frac{1}{2}{E}_{\mathrm{Q}\overline{\mathrm{Q}}}$ holds. The same is also true for the screening lengths whose values are in agreement with lattice QCD.

In this work we derive the Bekenstein-Hawking entropy formula, $S=\frac{A}{4l_p^2}$, from the following minimal assumptions: (i) there is a minimum area, $A_{\min }$, proportional to $l_p^2$; (ii) the event horizon area, $A$, is tessellated by $N=A/A_{\min }$ distinguishable units; and (iii) the internal structure of these units is that of an infinite tower of internal levels. Although our results are model independent, this internal structure can be realized as the excitations of more fundamental entities such as, for instance, strings or loop quantum gravity spin networks. Even more, once the microstates of the black hole are taken to be singlets formed within the infinite tower of states describing the whole event horizon, the correction term $-\frac{3}{2}\log A$ emerges from our model. Finally, some comments regarding the applicability of the present model to extremal black holes, as well as possible relationships with spectral geometry and other approaches are pointed out. Our results are independent of the dimension of the black hole and whether it is rotating or not.

We study the effects of a fixed de Sitter geometry background in scenarios of false vacuum decay. It is currently understood that bubble nucleation processes associated with first order phase transitions are particularly important in cosmology. Considering the geometry of spacetime complicates the interpretation of the decay rate of a metastable vacuum. However, the effects of curvature can still be studied in the particular case where backreaction is neglected. We compute the imaginary part of the action in de Sitter space, including the one-loop and the gradient corrections. We use two independent methodologies and quantify the size of the corrections without any assumptions on the thickness of the wall of the scalar background configuration.

Inspired by the observations of the supermassive black hole M87* by the Event Horizon Telescope (EHT), a remarkable surge in black hole physics is to use the black hole shadow’s observables to distinguish between general relativity and modified theories of gravity, which could also help to reveal the astrophysical nature of the central black hole in the EHT observation. In this paper, we study a charged rotating black hole in conformal gravity, in which the term related to the charge has different falloffs from the usual Kerr-Newman (KN) black hole. We investigate the spacetime properties including the horizons, ergospheres, and photon regions; then, we show the boundary of the black hole shadow and investigate its characteristic observables. These features closely depend on the spin and charge parameters, which are compared with those in Kerr and KN black holes. Then, presupposing that M87* is a charged rotating black hole in conformal gravity, we constrain the black hole parameters via the observational constraints from EHT. We find that the constraints on the inferred circularity deviation ($\mathrm{\Delta }C\lesssim 0.1$) and shadow axial ratio ($1<D_x\lesssim 4/3$) for M87* are satisfied for the entire parameter space of the charged rotating black hole in conformal gravity. However, the shadow angular diameter ${\theta }_d=42\pm 3\mu \mathrm{as}$ gives an upper bound on the parameter space. Our findings indicate that the current charged rotating black hole in conformal gravity could be a candidate for astrophysical black holes. Moreover, the EHT observation of the axial ratio $D_x$ may help us to distinguish between a Kerr black hole and the current charged rotating black hole in conformal gravity in some parameter space.

We study the dynamics of charged, spherically symmetric dust shells in the presence of a positive cosmological constant. We find generalizations of the well-known solutions in asymptotically flat spacetime, in particular orbits into “parallel universes,” but also new solutions corresponding to a “bounce” of the shell before an event horizon has formed. We also discuss “bubble” solutions, in which a charged shell and an oppositely charged singularity are spontaneously created and annihilated.

We study the observation of a stochastic gravitational-wave background (SGWB) made by a pulsar-timing array in the spherical harmonic space of the observable. The observable is a timing residual which is the time-averaged redshift fluctuation of a pulsar over the duration of observation. Using the Sachs-Wolfe line-of-sight integral for the redshift fluctuation, we derive the power spectrum of the timing residual, from which we develop a fast algorithm to compute the overlap reduction functions for the SGWB intensity and polarization anisotropies. We find that the algorithm is less complicated and more efficient than our previous work which is based on the expansion of the polarization basis tensors in terms of spherical harmonics. Also, we use the power spectrum to construct the bipolar spherical harmonic coefficients that characterize the statistical isotropy of the SGWB. In particular, the coefficients for the linear-polarization anisotropy are worked out for the first time. Our harmonic-space method is useful for the data analysis in future pulsar-timing-array observation on a large number of pulsars as well as for the measurement of the statistical isotropy of the SGWB.

The dark matter (DM) distributed around an intermediate massive black hole (IMBH) forms an overdensity region called DM minispike. We consider the binary system which consists of an IMBH with DM minispike and a small black hole inspiralling around the IMBH in eccentric orbits. The factors which affect the evolution of the orbit include the gravity of the system, the dynamical friction and accretion of the small black hole caused by the DM minispike, and the radiation reaction of gravitational waves (GWs). Using the method of osculating orbit, we find that when the semi-latus rectum $p\ll {10}^5{R}_s$ ($R_s$ is the Schwarzschild radius of the IMBH) the dominated factors are the dynamical friction and accretion from the DM minispike, and the radiation reaction. When $p\gg {10}^5{R}_s$, the gravity from the DM minispike dominates the orbital evolution. The existence of DM minispike leads to the deviation from the Keplerian orbit, such as extra orbital precession, henceforth extra phase shift in the GW waveform. By calculating the signal-to-noise ratio for GWs with and without DM minispikes and the mismatch between them, we show that the effect of the DM minispike in GW waveforms can potentially be detected by future space-based GW detectors such as LISA, Taiji, and Tianqin.

In this paper, we investigate the generalized covariant entropy bound in the theory where the Einstein gravity is perturbed by the higher-order Lovelock terms. After choosing the light sheet that is smooth under the perturbation limit, replacing the Bekenstein-Hawking entropy with the Jacobson-Myers entropy, and introducing two reasonable physical assumptions, we show that the corresponding generalized covariant entropy bound is satisfied under a higher-order approximation of the perturbation from the higher-order Lovelock terms. Our result implies that the Jacobson-Myers entropy strictly obeys the entropy bound under the perturbation level, and the generalized second law of Lanczos-Lovelock gravity is also satisfied when the Einstein gravity is perturbed by the higher-order Lovelock terms.

A novel structure-preserving algorithm for general relativity in vacuum is derived from a lattice gauge theoretic discretization of the tetradic Palatini action. The resulting model of discrete gravity is demonstrated to preserve local Lorentz invariance and symplectic structure.

This paper presents a novel quantum walk approach to simulating parton showers on a quantum computer. We demonstrate that the quantum walk paradigm offers a natural and more efficient approach to simulating parton showers on quantum devices, with the emission probabilities implemented as the coin flip for the walker, and the particle emissions to either gluons or quark pairs corresponding to the movement of the walker in two dimensions. A quantum algorithm is proposed for a simplified, toy model of a 31-step, collinear parton shower, hence significantly increasing the number of steps of the parton shower that can be simulated compared to previous quantum algorithms. Furthermore, it scales efficiently: the number of possible shower steps increases exponentially with the number of qubits, and the circuit depth grows linearly with the number of steps. Reframing the parton shower in the context of a quantum walk therefore brings dramatic improvements, and is a step towards extending the current quantum algorithms to simulate more realistic parton showers.

The study of the Higgs boson properties offers compelling perspectives for testing the effects of physics beyond the Standard Model and has deep implications for the LHC program and future colliders. Accurate determinations of the Higgs boson properties can provide us with a distinctively precise picture of the Higgs sector, set tight bounds, and predict ranges for the values of new physics model parameters. In this paper, we discuss the constraints on supersymmetry that can be derived by a determination of the Higgs boson mass and couplings. We quantify these constraints by using scans of the 19-parameter space of the so-called phenomenological minimal supersymmetric Standard Model. The fraction of scan points that can be excluded by the Higgs measurements is studied for the coupling measurement accuracies obtained in LHC run 2 and expected for the HL-LHC program and $e^{+}{e}^{-}$ colliders and contrasted with those derived from missing transverse energy searches at the LHC and from dark matter experiments.

Recently, the CDF collaboration reported a new measurement of the $W$ boson mass $M_W=80.4335\pm 0.0094\mathrm{GeV}$, which shows a $\sim 7\sigma$ deviation from the standard model prediction $80.3545\pm 0.0057\mathrm{GeV}$ obtained by the electroweak (EW) global fit. This deviation can be explained by new physics generating moderate EW oblique parameters $S$, $T$, and $U$. In this work, we use the loop corrections induced by some extra EW multiplets to explain the CDF $M_W$ anomaly. The lightest neutral particle in the multiplets can also serve as a candidate of cold dark matter (DM). We consider two such models, namely singlet-triplet scalar DM and singlet-doublet fermionic DM models, and perform numerical scans to find the parameter points accounting for the $M_W$ anomaly. The constraints from the correct DM thermal relic density and direct detection are also taken into account. We find the parameter points simultaneously interpreting the $M_W$ anomaly and satisfying the DM requirements in the former model, but do not find such parameter points in the latter model.

Recently, the RHICf Collaboration measured the transverse single-spin asymmetries of the very forward neutral pion in polarized $p+p$ collisions at $\sqrt{s}=510\mathrm{GeV}$, produced at large pseudorapidity ($\eta \gtrsim 6$). The data show large asymmetries both in longitudinal momentum fraction $x_F$ and transverse momentum $p_T$ at $p_T<1\mathrm{GeV}/c$. Employing baryonic triple Regge exchanges, we describe the complete RHICf data for the first time and show that the neutral pion production at low $p_T$ can be interpreted as a diffractive one.

$CP$ violation in $\mathrm{\Delta }{A}_{\mathrm{CP}}=-0.154(29)$, in the $D^0\to {\pi }^{+}{\pi }^{-}/K^{+}{K}^{-}$ system, is established, and its central value is 1 order of magnitude above the naive Standard Model (SM) estimate. It remains unclear whether this is due to currently incalculable strong interaction matrix elements or genuine new physics, such as a shift in ${\mathcal{O}}_8$ with a weak phase. We show that interference of the long-distance (LD) terms with the ${\mathcal{O}}_8$ matrix element can give rise to $A_{CP}^{D\to V\gamma }=\mathrm{few}\times {10}^{-3}$ (for reference values $\mathrm{Im}[C_8^{\mathrm{NP}}]\approx {10}^{-3}$). In addition, it is pointed out that the ratio of left- to right-handed (photon polarization) LD amplitudes is measurable in time-dependent $CP$ asymmetries. We argue that both theory and experimental consideration favor weak annihilation (WA) as the dominant LD contribution. More definite progress could be achieved by either computing the radiative corrections to WA or the measurement of the charged modes $D_{(d,s)}^{+}\to (\rho ,K^{*}{)}^{+}\gamma$ and $D_s\to {\rho }^{+}\gamma$.

Recently, the Belle Collaboration has measured the ${\mathrm{\Lambda }}_c^{+}\to \eta \mathrm{\Lambda }{\pi }^{+}$ decay and reported the $\eta \mathrm{\Lambda }$ and $\mathrm{\Lambda }{\pi }^{+}$ invariant mass distributions, which show the clear signals of the resonances $\mathrm{\Lambda }(1670)$ and $\mathrm{\Sigma }(1385)$, respectively. Based on our previous works [Eur. Phys. J. C 76, 496 (2016) and Phys. Rev. D 95, 074024 (2017)], we reanalyze this process by considering the $S$-wave $\eta \mathrm{\Lambda }$ and $\eta {\pi }^{+}$ final state interactions within the chiral unitary approach, which dynamically generate the $\mathrm{\Lambda }(1670)$ and $a_0(980)$, respectively. Our results are in agreement with the Belle measurements of the $\eta \mathrm{\Lambda }$ and ${\pi }^{+}\mathrm{\Lambda }$ invariant mass distributions. In addition, the ${\pi }^{+}\eta$ invariant mass distribution is also calculated and a cusp structure of $a_0(980)$ is clearly shown around the $K\overline{K}$ mass threshold.

We study the three-dimensional transport theory of massive spin-$1/2$ fermions resulting from the vorticity dependent quantum kinetic equation. This quantum kinetic equation has been introduced to take account of noninertial properties of rotating coordinate frames. We show that it is the appropriate relativistic kinetic equation which provides the vorticity dependent semiclassical transport equations of the three-dimensional Wigner function components. We establish the semiclassical kinetic equations of a linearly independent set of components. By means of them, kinetic equations of the chiral scalar distribution functions are derived. They furnish the 3D kinetic theory which permits us to study the vector and axial vector current densities by focusing on the mass corrections to the chiral vortical and separation effects.