In this paper, we simulate Super-Eddington accreting massive black holes (SEAMBHs) as the candles to probe cosmology for the first time. SEAMBHs have been demonstrated to be able to provide a new tool for estimating cosmological distance. Thus, we create a series of mock data sets of SEAMBHs, especially in the high redshift region, to check their abilities to probe the cosmology. To fulfill the potential of the SEAMBHs on the cosmology, we apply the simulated data to three projects. The first is the exploration of their abilities to constrain the cosmological parameters, in which we combine different data sets of current observations such as the cosmic microwave background from Planck and type Ia supernovae from Joint Light-curve Analysis (JLA). We find that the high redshift SEAMBHs can help to break the degeneracies of the background cosmological parameters constrained by Planck and JLA, thus giving much tighter constraints of the cosmological parameters. The second uses the high redshift SEAMBHs as the complements of the low redshift JLA to constrain the early expansion rate and the dark energy density evolution in the cold dark matter frame. Our results show that these high redshift SEAMBHs are very powerful on constraining the early Hubble rate and the evolution of the dark energy density; thus they can give us more information about the expansion history of our Universe, which is also crucial for testing the $\mathrm{\Lambda }\mathrm{CDM}$ model in the high redshift region. Finally, we check the SEAMBH candles’ abilities to reconstruct the equation of state for dark energy at high redshift. In summary, our results show that the SEAMBHs, as the rare candles in the high redshift region, can provide us a new and independent observation to probe cosmology in the future.

The decay of ${\mathrm{\Lambda }}_c^{+}$ into ${\pi }^{+}{\pi }^0\mathrm{\Lambda }(1405)$ with the $\mathrm{\Lambda }(1405)$ decay into ${\pi }^0{\mathrm{\Sigma }}^0$ through a triangle diagram is studied. This process is initiated by ${\mathrm{\Lambda }}_c^{+}\to {\pi }^{+}{\overline{K}}^{*}N$, and then the ${\overline{K}}^{*}$ decays into $\overline{K}\pi$ and $\overline{K}N$ produce the $\mathrm{\Lambda }(1405)$ through a triangle loop containing ${\overline{K}}^{*}N\overline{K}$ which develops a singularity around 1890 MeV. This process is prohibited by the isospin symmetry, but the decay into this channel is enhanced by the contribution of the triangle diagram, which is sensitive to the mass of the internal particles. We find a narrow peak in the ${\pi }^0{\mathrm{\Sigma }}^0$ invariant mass distribution, which originates from the $\mathrm{\Lambda }(1405)$ amplitude, but is tied to the mass differences between the charged and neutral $\overline{K}$ or $N$ states. The observation of the unavoidable peak of the triangle singularity in the isospin-violating $\mathrm{\Lambda }(1405)$ production would provide further support for the hadronic molecular picture of the $\mathrm{\Lambda }(1405)$ and further information on the $\overline{K}N$ interaction.

Density profiles of ultralight Bose-condensate dark matter inferred from numerical simulations of structure formation, ruled by the Gross-Pitaevskii-Poisson (GPP) system of equations, have a core-tail structure. Multistate equilibrium configurations of the GPP system, on the other hand, have a similar core-tail density profile. We now submit these multistate configurations to highly dynamical scenarios and show their potential as providers of appropriate density profiles of structures. We present the simulation of head-on collisions between two equilibrium configurations of the GPP system of equations, including the collision of ground state with multistate configurations. We study the regimes of solitonic and merger behavior and show generic properties of the dynamics of the system, including the relaxation process and attractor density profiles. We show that the merger of multistate configurations has the potential to produce core-tail density profiles, with the core dominated by the ground state and the halo dominated by an additional state.

We study the modular symmetry in magnetized D-brane models on $T^2$. Non-Abelian flavor symmetry $D_4$ in the model with magnetic flux $M=2$ (in a certain unit) is a subgroup of the modular symmetry. We also study the modular symmetry in heterotic orbifold models. The $T^2/Z_4$ orbifold model has the same modular symmetry as the magnetized brane model with $M=2$, and its flavor symmetry $D_4$ is a subgroup of the modular symmetry.

We investigate the phenomenon of electron-positron pair production from vacuum in the presence of a strong electric field superimposed by a weak but fast varying pulse which substantially increases the total particle yield. We employ a nonperturbative numerical technique and perform the calculations beyond the spatially-uniform-field approximation, i.e., dipole approximation, taking into account the coordinate dependence of the fast component. The analysis of the main characteristics of the pair-production process (momentum spectra of particles and total amount of pairs) reveals a number of important features which are absent within the previously used approximation. In particular, the structure of the momentum distribution is modified both qualitatively and quantitatively, and the total number of pairs created as well as the enhancement factor due to dynamical assistance become significantly smaller.

Due to shielding, direct detection experiments are in some cases insensitive to dark matter candidates with very large scattering cross sections with nucleons. In this paper, we revisit this class of models and derive a simple analytic criterion for conservative but robust direct detection limits. While large spin-independent cross sections seem to be ruled out, we identify potentially viable parameter space for dark matter with a spin-dependent cross section with nucleons in the range of ${10}^{-27}{\mathrm{cm}}^2\lesssim {\sigma }_{\mathrm{DM}-p}\lesssim {10}^{-24}{\mathrm{cm}}^2$. With these parameters, cosmic-ray scattering with dark matter in the extended halo of the Milky Way could generate a novel and distinctive gamma-ray signal at high galactic latitudes. Such a signal could be observable by Fermi or future space-based gamma-ray telescopes.

There is a common belief that the main uncertainties in the theoretical analysis of neutrinoless double beta ($0\nu \beta \beta$) decay originate from the nuclear matrix elements. Here, we uncover another previously overlooked source of potentially large uncertainties stemming from nonperturbative QCD effects. Recently perturbative QCD corrections have been calculated for all dimension 6 and 9 effective operators describing $0\nu \beta \beta$-decay and their importance for a reliable treatment of $0\nu \beta \beta$-decay has been demonstrated. However, these perturbative results are valid at energy scales above $\sim 1\mathrm{GeV}$, while the typical $0\nu \beta \beta$ scale is about $\sim 100\mathrm{MeV}$. In view of this fact we examine the possibility of extrapolating the perturbative results towards sub-GeV nonperturbative scales on the basis of the QCD coupling constant “freezing” behavior using background perturbation theory. Our analysis suggests that such an infrared extrapolation does modify the perturbative results for both short-range and long-range mechanisms of $0\nu \beta \beta$-decay in general only moderately. We also discuss that the $\text{tensor}\otimes \text{tensor}$ effective operator cannot appear alone in the low energy limit of any renormalizable high-scale model and then demonstrate that all five linearly independent combinations of the scalar and tensor operators, which can appear in renormalizable models, are infrared stable.

Neutral gauge bosons beyond the Standard Model are becoming interesting as possible mediators to explain several experimental anomalies. They have small masses, below 1 GeV, and are referred to as dark photons, $U$, $A^{\prime }$ or $Z^{\prime }$ bosons. Electron-positron collision experiments at the B-factories provide the most straightforward way to probe bosons of this kind. In the present article, we study production of the bosons at $e^{+}{e}^{-}$ colliders operating at GeV center-of-mass energies. We have studied two channels: $e^{+}{e}^{-}\to \gamma Z^{\prime }$ and $e^{+}{e}^{-}\to e^{+}{e}^{-}{Z}^{\prime }$. Analytic expressions for the cross sections and various observables such as the energy spectra of the produced bosons and the final electrons from the $Z^{\prime }$ decays are derived. We have also studied the transverse momentum distribution of the bosons and the spatial distribution of the $Z^{\prime }\to e^{+}{e}^{-}$ decay vertices. It is shown that these distributions provide distinct signatures of the bosons in $e^{+}{e}^{-}\to \gamma Z^{\prime }$. The reaction $e^{+}{e}^{-}\to e^{+}{e}^{-}{Z}^{\prime }$ becomes important at small $Z^{\prime }$ scattering angles where its contribution to the overall yield may be larger by orders of magnitude compared to $e^{+}{e}^{-}\to \gamma Z^{\prime }$. The standard processes $e^{+}{e}^{-}\to \gamma \gamma$ and $e^{+}{e}^{-}\to e^{+}{e}^{-}\gamma$ that lead to the same signal are considered. We include numerical predictions for the production rates at the energy $\sqrt{s}=10.5\mathrm{GeV}$. The case with a light scalar boson is also discussed. The calculations are performed in detail and can be useful for additional studies.

We propose a hidden gauged $U(1{)}_H$ $Z^{\prime }$ model to explain deviations from the standard model (SM) values in lepton flavor universality known as $R_K$ and $R_D$ anomalies. The $Z^{\prime }$ only interacts with the SM fermions via their mixing with vectorlike doublet fermions after the $U(1{)}_H$ symmetry breaking, which leads to $b\to s\mu \mu$ transition through the $Z^{\prime }$ at tree level. Moreover, introducing an additional mediator, inert-Higgs doublet, yields $b\to c\tau \nu$ process via charged scalar contribution at tree level. Using flavio package, we scrutinize adequate sizes of the relevant Wilson coefficients to these two processes by taking various flavor observables into account. It is found that significant mixing between the vectorlike and the second generation leptons is needed for the $R_K$ anomaly. A possible explanation of the $R_D$ anomaly can also be simultaneously addressed in a motivated situation, where a single scalar operator plays a dominant role, by the successful model parameters for the $R_K$ anomaly.

We argue that in order to account for the muon anomalous magnetic moment $g-2$, dark matter and LHC data, nonuniversal gaugino masses $M_i$ at the high scale are required in the framework of the minimal supersymmetric standard model. We also need a right-handed smuon ${\tilde{\mu }}_R$ with a mass around 100 GeV, evading LHC searches due to the proximity of a neutralino ${\tilde{\chi }}_1^0$ several GeV lighter which allows successful dark matter. We discuss such a scenario in the framework of an $SU(5)$ grand unified theory (GUT) combined with $A_4$ family symmetry, where the three $\overline{5}$ representations form a single triplet of $A_4$ with a unified soft mass $m_F$, while the three 10 representations are singlets of $A_4$ with independent soft masses $m_{T1},m_{T2},m_{T3}$. Although $m_{T2}$ (and hence ${\tilde{\mu }}_R$) may be light, the muon $g-2$ and relic density also requires light $M_1\simeq 250\mathrm{GeV}$, which is incompatible with universal gaugino masses due to LHC constraints on $M_2$ and $M_3$ arising from gaugino searches. After showing that universal gaugino masses $M_{1/2}$ at the GUT scale are excluded by gluino searches, we provide a series of benchmarks which show that while $M_1=M_2\ll M_3$ is in tension with 8 and 13 TeV LHC data, $M_1<M_2\ll M_3$ is currently allowed. Even this scenario is almost excluded by the tension between the muon $g-2$, relic density, dark matter direct detection and LHC data. We focus on a region of parameter space that has not been studied in detail before being characterized by low Higgsino mass $\mu \approx -300\mathrm{GeV}$, as required by the muon $g-2$. The LHC will be able to fully test this scenario with the upgraded luminosity via muon-dominated tri- and dilepton signatures resulting from Higgsino-dominated ${\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_2^0$ and ${\tilde{\chi }}_1^{+}{\tilde{\chi }}_1^{-}$ production.

We consider the heavy-dense limit of QCD at finite fermion density in the canonical formulation and approximate it by a three-state Potts model. In the strong-coupling limit, the model is free of the sign problem. Away from the strong coupling, the sign problem is solved by employing a cluster algorithm which allows to average each cluster over the $\mathbb{Z}(3)$ sectors. Improved estimators for physical quantities can be constructed by taking into account the triality of the clusters, that is, their transformation properties with respect to $\mathbb{Z}(3)$ transformations.

We investigate the phase structure of SU(4) gauge theory with the gauge field simultaneously coupled to two flavors of fermions in the fundamental representation and two flavors of fermions in the two-index antisymmetric representation. We find that the theory has only two phases: a low-temperature phase with both species of fermion confined and chirally broken, and a high-temperature phase with both species of fermion deconfined and chirally restored. The single phase transition in the theory appears to be first order, in agreement with theoretical predictions.

We compute the running of the coupling in SU(2) gauge theory with six fermions in the fundamental representation of the gauge group. We find strong evidence that this theory has an infrared stable fixed point at strong coupling and measure also the anomalous dimension of the fermion mass operator at the fixed point. This theory therefore likely lies close to the boundary of the conformal window and will display novel infrared dynamics if coupled with the electroweak sector of the Standard Model.

In order to explore the possible physical quantities for judging different structures of the newly observed resonance $d^{*}(2380)$, we study its electromagnetic form factors. In addition to the electric charge monopole $C0$, we calculate its electric quadrupole $E2$, magnetic dipole $M1$, and magnetic octupole $M3$ form factors on the base of the realistic coupled $\mathrm{\Delta }\mathrm{\Delta }+C_8{C}_8$ channel $d^{*}$ wave function with both the $S$- and $D$-partial waves. The results show that the magnetic dipole moment and electric quadrupole deformation of $d^{*}$ are 7.602 and $2.53\times {10}^{-2}{\mathrm{fm}}^2$, respectively. The calculated magnetic dipole moment in the naive constituent quark model is also compared with the result of $D_{12}\pi$ picture. By comparing with partial results where the $d^{*}$ state is considered with a single $\mathrm{\Delta }\mathrm{\Delta }$ and with a $D_{12}\pi$ structures, we find that in addition to the charge distribution of $d^{*}$, the magnetic dipole moment and magnetic radius can be used to discriminate different structures of $d^{*}$. Moreover, a quite small electric quadrupole deformation indicates that $d^{*}$ is more inclined to a slightly oblate shape due to our compact hexaquark dominated structure of $d^{*}$.

Using tangent bundle geometry we construct an equivalent reformulation of classical field theory on flat spacetimes which simultaneously encodes the perspectives of multiple observers. Its generalization to curved spacetimes realizes a new type of nonminimal coupling of the fields and is shown to admit a canonical quantization procedure. For the resulting quantum theory we demonstrate the emergence of a particle interpretation, fully consistent with general relativistic geometry. The path dependency of parallel transport forces each observer to carry their own quantum state; we find that the communication of the corresponding quantum information may generate extra particles on curved spacetimes. A speculative link between quantum information and spacetime curvature is discussed which might lead to novel explanations for quantum decoherence and vanishing interference in double-slit or interaction-free measurement scenarios, in the mere presence of additional observers.

We consider a traversable wormhole solution of Einstein’s gravity conformally coupled to a massless scalar field, a solution derived by Barcelo and Visser based on the Janis-Newman-Winicour-Wyman spacetime. We study the geodesic motion of timelike, lightlike, and spacelike particles in this spacetime. We solve the equations of motion analytically in terms of the Weierstraß functions and discuss all possible orbit types and their parameter dependence. Interestingly, bound orbits occur for timelike geodesics only in one of the two worlds. Moreover, under no conditions there exist timelike two world bound orbits.

In this paper, the ghost-freeness of the higher derivative theory proposed by Hassan et al. in [Universe 1, 92 (2015)] is investigated. Hassan et al. believed the ghost-freeness of the higher derivative theory based on the analysis in the linear approximation. However, in order to obtain the complete correspondence, we have to analyze the model without any approximations. In this paper, we analyze the two-scalar model proposed in [Universe 1, 92 (2015)] with arbitrary nonderivative interaction terms. In any order with respect to perturbative parameters, we prove that we can eliminate the ghost for the model with any nonderivative interaction terms.

We analyze the scalar potential of the simplest little Higgs (SLH) model in an approach consistent with the spirit of continuum effective field theory (CEFT). By requiring correct electroweak symmetry breaking (EWSB) with the 125 GeV Higgs boson, we are able to derive a relation between the pseudoaxion mass $m_{\eta }$ and the heavy top mass $m_T$, which serves as a crucial test of the SLH mechanism. By requiring $m_{\eta }^2>0$ an upper bound on $m_T$ can be obtained for any fixed SLH global symmetry breaking scale $f$. We also point out that an absolute upper bound on $f$ can be obtained by imposing partial wave unitarity constraint, which in turn leads to absolute upper bounds of $m_T\lesssim 19\mathrm{TeV}$, $m_{\eta }\lesssim 1.5\mathrm{TeV}$, and $m_{Z^{\prime }}\lesssim 48\mathrm{TeV}$. We present the allowed region in the three-dimensional parameter space characterized by $f,t_{\beta },m_T$, taking into account the requirement of valid EWSB and the constraint from perturbative unitarity. We also propose a strategy of analyzing the fine-tuning problem consistent with the spirit of CEFT and apply it to the SLH. We suggest that the scalar potential and fine-tuning analysis strategies adopted here should also be applicable to a wide class of little Higgs and twin Higgs models, which may reveal interesting relations as crucial tests of the related EWSB mechanism and provide a new perspective on assessing their degree of fine-tuning.

Through the embedding of superconformal quantum mechanics into AdS space, it is possible to construct an effective supersymmetric QCD light-front Hamiltonian for hadrons, which includes a spin-spin interaction between the hadronic constituents. A specific breaking of conformal symmetry determines a unique effective quark-confining potential for light hadrons, as well as remarkable connections between the meson, baryon, and tetraquark spectra. The pion is massless in the chiral limit and has no supersymmetric partner. The excitation spectra of relativistic light-quark meson, baryon and tetraquark bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. Although conformal symmetry is strongly broken by the heavy quark mass, the basic underlying supersymmetric mechanism, which transforms mesons to baryons (and baryons to tetraquarks) into each other, still holds and gives remarkable connections across the entire spectrum of light, heavy-light and double-heavy hadrons. Here we show that all the observed hadrons can be related through this effective supersymmetric QCD, and that it can be used to identify the structure of the new charmonium states.