The ANtarctic Impulsive Transient Antenna (ANITA) Collaboration has observed two EeV-energy, upward-going events originating from below the horizon. As no standard-model (SM) particles propagating through the Earth at such energy and exit angles can give rise to the required survival probability for the observed events, several beyond-standard-model (BSM) proposals have come up. We propose a scenario where a $Z_2$-odd sector is responsible for such anomalous events. The next-to-lightest $Z_2$-odd particle or the next-to-lightest stable particle (NLSP), created from ultrahigh-energy neutrino interactions with nucleons, can pass through the Earth and then decay into the lightest $Z_2$-odd particle or the lightest stable particle (LSP) and a tau lepton. The long-lived nature of the NLSP requires its coupling with the LSP to be very small, keeping the LSP out of thermal equilibrium in the early Universe. The LSP can then be a nonthermal dark matter, while the tau leptons produced from NLSP decay after passing through Earth can explain the ANITA events. We first show that a purely nonthermal dark matter scenario cannot give rise to the required event rates, while a hybrid scenario where dark matter can have thermal as well as nonthermal contribution to its relic abundance serves the purpose.

A dynamical quantum simulation of SU(2) non-Abelian gauge field theory on a digital quantum computer is presented. This was enabled on current quantum hardware by introducing a mapping of the field onto a register of qubits that utilizes local gauge symmetry while preserving local constraints on the fields, reducing the dimensionality of the calculation. Controlled plaquette operators and gauge-variant completions in the unphysical part of the Hilbert space were designed and used to implement time evolution. The new techniques developed in this work generalize to quantum simulations of higher dimensional gauge field theories.

We study the bottom ${\mathrm{\Lambda }}_b(6146{)}^0$ baryon, newly discovered by the LHCb Collaboration. By adopting an interpolating current of $(L_{\rho },L_{\lambda })=(0,2)$ type and $D$-wave nature with spin-parity quantum numbers $J^P={\frac{3}{2}}^{+}$ for this heavy bottom baryon, we calculate its mass and residue. Using these spectroscopic parameters, we also investigate its dominant decays ${\mathrm{\Lambda }}_b(6146{)}^0\to {\mathrm{\Sigma }}_b\pi$ and ${\mathrm{\Lambda }}_b(6146{)}^0\to {\mathrm{\Sigma }}_b^{*}\pi$ and estimate the width of ${\mathrm{\Lambda }}_b(6146{)}^0$ obtained via these channels. The obtained mass, $m_{{\mathrm{\Lambda }}_b}=(6144\pm 68)\mathrm{MeV}$ is in accord nicely with the experimental data. The width obtained via the dominant channels is also consistent with the experimental data of LHCb collaboration. We calculate the spectroscopic parameters and the same decay channels for the $c$-partner of ${\mathrm{\Lambda }}_b(6146{)}^0$ state, namely ${\mathrm{\Lambda }}_c(2860{)}^{+}$, as well. We compare the obtained results with the existing theoretical predictions as well as experimental data. The results indicate that the state ${\mathrm{\Lambda }}_b(6146{)}^0$ and its charmed-partner ${\mathrm{\Lambda }}_c(2860{)}^{+}$ can be considered as $1D$-wave baryons with $J^P={\frac{3}{2}}^{+}$.

The potential for probing extra neutral gauge boson mediators ($Z^{\prime }$) from low-energy measurements is comprehensively explored. Our study mainly focuses on $Z^{\prime }$ mediators present in string-inspired $E_6$ models and left-right symmetry. We estimate the sensitivities of coherent-elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) and neutrino-electron scattering experiments. Our results indicate that such low-energy high-intensity measurements can provide a valuable probe, complementary to high-energy collider searches and electroweak precision measurements.

We generalize the celebrated heavy quark expansion to nonlocal QCD operators. By taking nonlocal heavy-light current on the light-cone as an example, we confirm that the collinear singularities are common between QCD operator and the corresponding operator in heavy quark effective theory (HQET), at the leading power of $1/M$ expansion. Based on a perturbative calculation in operator form at one-loop level, a factorization formula linking QCD and HQET operators is investigated and the matching coefficient is determined. The matching between QCD and HQET light-cone distribution amplitudes (LCDAs) as well as other momentum distributions of hadron can be derived as a consequence.

We study the gravitational wave phenomenology in models of solitosynthesis. In such models, a first order phase transition is precipitated by a period in which nontopological solitons with a conserved global charge (Q-balls) accumulate charge. As such, the nucleation rate of critical bubbles differs significantly from thermal phase transitions. In general we find that the peak amplitude of the gravitational wave spectrum resulting from solitosynthesis is stronger than that of a thermal phase transition, while the timescale of the onset of nonlinear plasma dynamics may be comparable to Hubble. We demonstrate this explicitly in an asymmetric dark matter model, and discuss current and future constraints in this scenario.

We calculate respectively, from the viewpoints of an instantaneously/locally inertial observer and a coaccelerated observer, the transition rates of the two-atom system in the symmetric/antisymmetric entangled state [$|{\psi }_{\pm }⟩$]. The scalar fields to which the atoms are coupled are respectively assumed to be in the vacuum state and a thermal state in the instantaneously inertial frame and in the coaccelerated frame. We show that both the upward transition $|{\psi }_{\pm }⟩\to |e_A{e}_B⟩$ and the downward transition $|{\psi }_{\pm }⟩\to |g_A{g}_B⟩$ take place, where $|g_A{g}_B⟩$ and $|e_A{e}_B⟩$ represent two collective eigenstates of the two-atom system with both atoms in their ground state and excited state respectively, and the transition rates observed in the two frames are identical only if there exists a thermal bath at the Fulling-Davies-Unruh temperature in the coaccelerated frame. Though both the downward and upward transition rates are characterized by the Plankian factor, this factor does not show up in the average variation rate of energy of the two-atom system, as a result of the perfect cancellation of the terms in the transition rates in the instantaneously inertial frame multiplied by the Plankian factor which corresponds to the Unruh thermal bath, and the cancellation of the temperature-dependent terms in the transition rates observed in the coaccelerated frame. A comparison of the transition rates of a static two-atom system in interaction with the massless scalar field in a thermal state at an arbitrary temperature with those of a uniformly accelerated two-atom system in interaction with the vacuum massless scalar field shows that the equivalence between the thermal bath and the uniform acceleration, which is well known to be valid for the single atom case, no longer holds for the two-atom system in the symmetric/antisymmetric entangled state. The effect of atomic uniform acceleration in the transition rates of the two-atom system, and the roles of both the downward and the upward transitions in the disentanglement of the two-atom system are also discussed.

Mirror symmetry is a type of infrared duality in three-dimensional (3D) quantum field theory that relates the low-energy dynamics of two distinct ultraviolet descriptions. Though first discovered in the supersymmetric context, it has far-reaching implications for understanding nonperturbative physics in general 3D quantum field theories. We study mirror symmetry in 3D $\mathcal{N}=4$ supersymmetric field theories whose Higgs or Coulomb branches realize $D$- and $E$-type Kleinian singularities in the $ADE$ classification, generalizing previous work on the $A$-type case. Such theories include the $SU(2)$ gauge theory coupled to fundamental matter in the $D$-type case and non-Lagrangian generalizations thereof in the $E$-type case. In these cases, the mirror description is given by a quiver gauge theory of affine $D$- or $E$-type. We investigate the mirror map at the level of the recently identified 1D protected subsector described by topological quantum mechanics, which implements a deformation quantization of the corresponding $ADE$ singularity. We give an explicit dictionary between the monopole operators and their dual mesonic operators in the $D$-type case. Along the way, we extract various operator product expansion coefficients for the quantized Higgs and Coulomb branches. We conclude by offering some perspectives on how the topological subsectors of the $E$-type quivers might shed light on their non-Lagrangian duals.

We study the influence of the cosmic expansion on the size of the shadow of a spinning black hole observed by a comoving observer. We first consider that the expansion is driven by a cosmological constant only and build the connection between the Kerr-de Sitter metric and the Friedmann–-Lemaître–-Robertson–-Walker metric. We clarify that the notion of a comoving observer is well defined in the spacetime of a spinning black hole only in the sense of being asymptotic. The angular size of the shadow for a comoving observer is calculated. Significantly we find that the angular size approaches a nonzero finite value for a distant comoving observer, while it vanishes for a distant static observer. Furthermore, by adopting the approximate method proposed in [G. S. Bisnovatyi-Kogan and O. Y. Tsupko, Phys. Rev. D 98, 084020 (2018).] we extend the study to the general multicomponent universe case. The results show that the difference between the horizontal and vertical angular size changes a lot, while their ratio, i.e., the oblateness, keeps unchanged when the supermassive spinning black hole is at a high redshift, due to the common amplification factor exerted by the cosmic expansion. In addition, when $a=0$, our results agree with the previous studies in [V. Perlick, O. Y. Tsupko, and G. S. Bisnovatyi-Kogan, Phys. Rev. D 97, 104062 (2018)., G. S. Bisnovatyi-Kogan and O. Y. Tsupko, Phys. Rev. D 98, 084020 (2018).].

We construct the spin-projection operators for a theory containing a symmetric two-index tensor and a general three-index tensor. We then use them to analyze, at linearized level, the most general action for a metric affine theory of gravity with terms up to second order in curvature, which depends on 28 parameters. In the metric case, we recover known results. In the torsion-free case, we are able to determine the most general six-parameter class of theories that are projective invariant, contain only one massless spin 2 and no spin 3, and are free of ghosts and tachyons.

We construct new, multivariate empirical relations for measuring neutron star radii and tidal deformabilities from the dominant gravitational wave frequency in the postmerger phase of binary neutron star mergers. The relations determine neutron star radii and tidal deformabilities for specific neutron star masses with consistent accuracy and depend only on two observables: the postmerger peak frequency $f_{\text{peak}}$ and the chirp mass $M_{\text{chirp}}$. The former could be measured with good accuracy from gravitational waves emitted in the postmerger phase using next-generation detectors, whereas the latter is already obtained with good accuracy from the inspiral phase with present-day detectors. Our main dataset consists of a gravitational wave catalog obtained with smoothed-particle hydrodynamics simulations within the spatial conformal flatness approximation. We also extract the $f_{\text{peak}}$ frequency from the publicly available CoRe data set, obtained through grid-based general-relativistic hydrodynamical simulations and find good agreement between the extracted frequencies of the two datasets. As a result, we can construct empirical relations for the combined datasets. Furthermore, we investigate empirical relations for two secondary peaks, $f_{2-0}$ and $f_{\text{spiral}}$, and show that these relations are distinct in the whole parameter space, in agreement with a previously introduced spectral classification scheme. Finally, we show that the spectral classification scheme can be reproduced using machine-learning techniques.

A ($3+1$)-dimensional Einstein-Gauss-Bonnet theory of gravity has been recently formulated by Glavan and Lin [D. Glavan and C. Lin, Phys. Rev. Lett. 124, 081301 (2020)] which is different from the pure Einstein theory, i.e., bypasses the Lovelock’s theorem and avoids Ostrogradsky instability. The theory was formulated in $D>4$ dimensions and its action consists of the Einstein-Hilbert term with a cosmological constant, while the Gauss-Bonnet term multiplied by a factor $1/(D-4)$. Then, the four-dimensional theory is defined as the limit $D\to 4$. Here we generalize this approach to the four-dimensional Einstein-Lovelock theory and formulate the most general static $4D$ black-hole solution allowing for a $\mathrm{\Lambda }$ term (either positive or negative) and the electric charge $Q$. As metric functions cannot be found in a closed form in the general case, we develop and share publicly the code which constructs the metric functions for every given set of parameters.

We revisit and clarify the gauge dependence of gravitational waves generated at second order from scalar perturbations. In a universe dominated by a perfect fluid with a constant equation-of-state parameter $w$, we compute the energy density of such induced gravitational waves in the Newtonian, comoving, and uniform curvature gauges. Huge differences are found between the Newtonian and comoving gauge results for any $w(\ge 0)$. This is always caused by the perturbation of the shift vector. Interestingly, the Newtonian and uniform curvature gauge calculations give the same energy density for $w>0$. In the case of $w=0$, the uniform curvature gauge result differs only by a factor from that of the comoving gauge, but it deviates significantly from that of the Newtonian gauge. Our calculation is done analytically for $w=0$ and $w=1/3$, and our result is consistent with the previous numerical one.

$SU(2)$ gauge fields and axions can have a stable, isotropic and homogeneous configuration during inflation. However, couplings to other matter species lead to particle production, which in turn induces backreaction on and destabilization of the non-Abelian and axion background. In this paper, we first study the particle production by a $SU(2)$ gauge field coupled to a massive Dirac doublet. To carry out this calculation we have made two technical improvements compared to what has been done in the literature. First, we apply the antisymmetrization of the operators to treat particles and antiparticles on equal footing; second, to deal with the UV divergences, we apply instantaneous subtraction. We find that the backreaction of produced fermions on the $SU(2)$ background is negligible for model parameters of observational interest. Next, we consider production of fermions due to coupling to the axion. The tree-level backreaction on the gauge fields, as well as on the axion, is vanishingly small. We also provide an estimate for the loop effects.

Ultra high energy cosmogenic neutrinos may represent a unique opportunity to unveil possible new physics interactions once restricted to the neutrino sector only. In the present paper we study the observable effects of a secret active-sterile interactions, mediated by a pseudoscalar, on the expected flux of cosmogenic neutrinos. The results show that for masses of sterile neutrinos and pseudoscalars of hundreds MeV, necessary to evade cosmological, astrophysical, and elementary particle constraints, the presence of such new interactions can significantly change the energy spectrum of cosmogenic neutrinos at Earth in the energy range from PeV to ZeV. Interestingly, the distortion of the spectrum results to be detectable at apparatus like GRAND or ARIANNA if the mediator mass is around 250 MeV and the UHECRs are dominated by the proton component. Larger mediator masses or a chemical composition of UHECRs dominated by heavier nuclei would require much larger cosmic rays apparatus which might be available in future.

Novelty detection is the machine learning task to recognize data, which belong to an unknown pattern. Complementary to supervised learning, it allows us to analyze data model-independently. We demonstrate the potential role of novelty detection in collider physics, using autoencoder-based deep neural network. Explicitly, we develop a set of density-based novelty evaluators, which are sensitive to the clustering of unknown-pattern testing data or new-physics signal events, for the design of detection algorithms. We also explore the influence of the known-pattern data fluctuations, arising from nonsignal regions, on detection sensitivity. Strategies to address it are proposed. The algorithms are applied to detecting fermionic ditop partner and resonant ditop productions at LHC, and exotic Higgs decays of two specific modes at a future $e^{+}{e}^{-}$ collider. With parton-level analysis, we conclude that potentially the new-physics benchmarks can be recognized with high efficiency.

We propose a simple model of noncommutative geometry to describe the structure of the standard model, which satisfies ${\mathrm{spin}}_c$ condition, has no fermion doubling, does not lead to the possibility of color symmetry breaking, and explains the $CP$ violation as the failure of the reality condition for the Dirac operator.

We explore the signatures of the ${\tilde{R}}_2$ class of leptoquark (LQ) models at the proposed $e^{-}p$ and $e^{+}p$ colliders. We carry out an analysis for the proposed colliders, LHeC, and FCC-eh, with center of mass (c.m.) energy 1.3 TeV and 3.46 TeV, respectively. For ${\tilde{R}}_2$ class of LQ models, there are a number of final states that can arise from LQs production and their subsequent decays. In this report we do a detailed cut-based analysis for the $l^{\pm }j$ final state. We also discuss the effect of polarized electron and positron beams on LQ production and in turn on $l^{\pm }j$ production. At LHeC, the final state $l^{+}j$ has a very good discovery prospect. We find that, with only $100{\mathrm{fb}}^{-1}$ of data, one can probe LQs of masses up to 1.2 TeV with $5\sigma$ significance, even with a generic set of cuts. On the contrary, at FCC-eh, one can probe LQ masses upto 2.2 TeV (for $e^{-}$ beam) and 3 TeV (for $e^{+}$ beam), at more than $5\sigma$ significance with luminosity $1000{\mathrm{fb}}^{-1}$ and $500{\mathrm{fb}}^{-1}$, respectively.