Several ideas exist on how the stringent mass limits from LHC on new colored particles can be avoided. One idea are the so-called “stealth” scenarios in which missing transversal energy (${\cancel{E}}_T$) is avoided due a peculiar mass configuration. It is usually assumed that the cascade decay of the dominantly produced colored particle finishes in a two-body decay, where this mass configuration leads to a very small amount of ${\cancel{E}}_T$. We discuss here the potential impact of other decay channels, either loop-induced or via off-shell mediators. It is shown that those channels already become important even for moderate branching ratios of 10%. Larger branching ratios, in particular, into a photon can completely wash out all benefits of the stealth setup. We discuss this in a model-independent form, but also at the simplest supersymmetry stealth scenario which can be realized in the next-to-minimal supersymmetric standard model.

We compute the next-to-leading order corrections to the cross section for the production of electroweak gauge bosons ($Z$, $W^{\pm }$ and ${\gamma }^{*}$) with large transverse momentum in double (longitudinally) polarized hadronic collisions. The calculation is fully performed in the ’t Hooft, Veltman, Breitenlohner, and Maison scheme within dimensional regularization with a careful treatment of issues arising due to the appearance of ${\gamma }^5$ in polarization projectors and axial couplings. We study the phenomenological consequences of the next-to-leading-order corrections at the level of both the double polarized cross section and the corresponding asymmetries at Relativist Heavy Ion Collider kinematics.

We study the existence of self-dual solitons in a gauged version of the baby Skyrme model in which the Maxwell-Chern-Simons term governs the gauge field dynamic. For such a purpose, a detailed implementation of the Bogomol’nyi-Prasad-Sommerfield formalism provides a lower bound for the energy and the respective self-dual equations. The energy lower bound is quantized because it is proportional to the topological charge of the Skyrme field. Furthermore, neither the magnetic flux nor the electric charge is quantized. We find two types of self-dual Skyrme field profiles: the first is described by a solution which follows a Gaussian decay law, and the second is portrayed by a solution having a power-law decay. For both types of skyrmion profiles, the asymptotic behavior of the respective gauge field is similar to the one for the Abrikosov-Nielsen-Olesen vortices. The localized inversion of the magnetic flux is another feature not observed in other gauged Skyrme models already studied in the literature.

Starting from an ultraviolet fixed point, we study the infrared behavior of quantum Weyl gravity in terms of a functional renormalization group (RG) flow equation. To do so, we employ two classes of Bach-flat backgrounds, namely maximally symmetric spacetimes and Ricci-flat backgrounds in the improved one-loop scheme. We show that in the absence of matter fields and with a topological term included, the effective action exhibits dynamical breaking of scale symmetry. In particular, it is shown that apart from a genuine IR fixed point that is reached at a zero value of the running scale, the RG flow also exhibits bouncing behavior in the IR regime. We demonstrate that both ${\beta }_C$ and ${\beta }_E$ reach the RG turning point (almost) simultaneously at the same finite energy scale, irrespective of the chosen background. The IR fixed point itself is found to be IR stable in the space of the considered couplings. Ensuing scaling dimensions of both operators are also computed. Salient issues, including the connection of the observed bouncing RG flow behavior with holography and prospective implications in early Universe cosmology, are also briefly discussed.

Effective-one-body (EOB) numerical-relativity (NR) waveform models for spin-aligned binary black holes (BBHs), known as the SEOBNR waveform models, are based on the EOB theoretical framework and NR simulations. SEOBNR models have played an important role in the LIGO Scientific Collaboration (LSC) gravitational wave (GW) data analysis for both signal search and parameter estimation. SEOBNR models for quasicircular orbits have evolved through version 1 to version 4 by extending their validity domain and including more NR results. Along another direction, we recently extended the SEOBNRv1 model to the SEOBNRE model which is valid for spin-aligned BBH coalescence along eccentric orbits. In this paper we validate this theoretical waveform model by comparing them against the NR simulation bank, simulating extreme spacetimes (SXS) catalog. In total, 278 NR waveforms are investigated which include binaries with large eccentricity; large spin and large mass ratio. Our SEOBNRE can model the NR waveforms quite well. The fitting factor for most of the 278 waveforms is larger than 99%. It indicates that the SEOBNRE model could be used as template waveforms for eccentric spin-aligned BBH coalescence. Moreover, we investigate the limitation in using circular BBH waveform templates in the Advanced LIGO and Einstein Telescope era.

We study image formation with the solar gravitational lens (SGL). We consider a point source that is positioned at a large but finite distance from the Sun. We assume that an optical telescope is positioned in the image plane, in the focal region of the SGL. We model the telescope as a convex lens and evaluate the intensity distribution produced by the electromagnetic field that forms the image in the focal plane of the convex lens. We first investigate the case when the telescope is located on the optical axis of the SGL or in its immediate vicinity. This is the region of strong interference where the SGL forms an image of a distant source, which is our primary interest. We derive analytic expressions that describe the progression of the image from an Einstein ring corresponding to an on-axis telescope position, to the case of two bright spots when the telescope is positioned some distance away from the optical axis. At greater distances from the optical axis, in the region of weak interference and that of geometric optics, we recover expressions that are familiar from models of gravitational microlensing, but developed here using a wave-optical treatment. We discuss applications of the results for imaging and spectroscopy of exoplanets with the SGL.

The gravitational wave observations of colliding black holes have opened a new window into the unexplored extreme gravity sector of physics, where the gravitational fields are immensely strong, nonlinear, and dynamical. Ten binary black hole merger events observed so far can be used to test Einstein’s theory of general relativity, which has otherwise been proven to agree with observations from several sources in the weak- or static-field regimes. One interesting future possibility is to detect gravitational waves from GW150914-like stellar-mass black hole binaries with both ground-based and space-based detectors. We here demonstrate the power of testing extreme gravity with such multiband gravitational-wave observations. In particular, we consider two theory-agnostic methods to test gravity using gravitational waves. The first test is the parametrized test where we introduce generic non-Einsteinian corrections to the waveform, which can easily be mapped to parameters in known example theories beyond general relativity. The second test is the inspiral-merger-ringdown consistency test where one derives the mass and spin of a merger remnant from the inspiral and merger-ringdown independently assuming general relativity is correct, and then check their consistency. In both cases, we use Fisher analyses and compare the results with Bayesian ones wherever possible. Regarding the first test, we find that multiband observations can be crucial in probing certain modified theories of gravity, including those with gravitational parity violation. Regarding the second test, we show that future single-band detections can improve upon the current tests by roughly 3 orders of magnitude, and further 7–10 times improvement may be realized with multiband observations.

Models in which scalar field dark energy interacts with dark matter via a pure momentum coupling have previously been found to potentially ease the structure formation tension between early and late-Universe observations. In this paper, we explore the physical mechanism underlying this feature. We argue analytically that the perturbation growth equations imply the suppression of structure growth, illustrating our discussion with numerical calculations. Then we generalize the previously studied quadratic coupling between the dark energy and dark matter to a more general power-law case, also allowing for the slope of the dark energy exponential potential to vary. We find that the structure growth suppression is a generic feature of power-law couplings and it can, for a range of parameter values, be larger than previously found.

Future galaxy clustering surveys will probe small scales where nonlinearities become important. Since the number of modes accessible on intermediate to small scales is very high, having a precise model at these scales is important especially in the context of discriminating alternative cosmological models from the standard one. In the mildly nonlinear regime, such models typically differ from each other, and galaxy clustering data will become very precise on these scales in the near future. As the observable quantity is the angular power spectrum in redshift space, it is important to study the effects of nonlinear density and redshift space distortion (RSD) in the angular power spectrum. We compute nonlinear contributions to the angular power spectrum using a flat-sky approximation, and compare the results of different perturbative and nonperturbative approaches. We find that the Taruya-Nishimichi-Saito (TNS) perturbative approach is significantly closer to the comoving Lagrangian acceleration approximation than Eulerian or partially resummed-Lagrangian one-loop approximations, effective field theory of large scale structure or a halofit-inspired model. However, none of these prescriptions agree with each other in the nonlinear regime. A surprising and new result of the present analysis is that for narrow redshift bins, $\mathrm{\Delta }z\lesssim 0.01$, the angular power spectrum acquires nonlinear contributions on all scales, right down to $\ell =2$, and is hence not a reliable tool at this time. To overcome this problem, we need to model nonlinear RSD terms, for example as TNS does, but for a matter power spectrum that remains reasonably accurate well into the deeply nonlinear regime, such as halofit.

We analytically calculate the scalar induced gravitational waves (SIGWs) and find a log-dependent slope of SIGW in the infrared regions $(f<f_c)$, namely $n_{\mathrm{GW}}(f)=3-2/\ln (f_c/f)$, and $n_{\mathrm{GW}}(f)=2-2/\ln (f_c/f)$ near the peak if the power spectrum of scalar curvature perturbation is quite narrow, where $f_c$ is roughly the peak frequency. Such a log-dependent slope can be taken as a new template for distinguishing SIGW from other sources.

Brownian thermal noise is a limiting factor for the sensitivity of many high precision metrology applications, among other gravitational-wave detectors. The origin of Brownian noise can be traced down to internal friction in the amorphous materials that are used for the high reflection coatings. To properly characterize the internal friction in an amorphous material, one needs to consider separately the bulk and shear losses. In most of previous works the two loss angles were considered equal, although without any first principle motivation. In this work we present a method that can be used to extract the material bulk and shear loss angles, based on current state-of-the-art coating ring-down measurement systems. We also show that for titania-doped tantala, a material commonly used in gravitational-wave detector coatings, the experimental data strongly favor a model with two different and distinct loss angles, over the simpler case of one single loss angle.

Multiparticle correlators are mathematical objects frequently encountered in quantum field theory and collider physics. By translating multiparticle correlators into the language of graph theory, we can gain new insights into their structure as well as identify efficient ways to manipulate them. We highlight the power of this graph-theoretic approach by “cutting open” the vertices and edges of the graphs, allowing us to systematically classify linear relations among multiparticle correlators and develop faster methods for their computation. The naive computational complexity of an $N$-point correlator among $M$ particles is $\mathcal{O}(M^N)$, but when the pairwise distances between particles can be cast as an inner product, we show that all such correlators can be computed in linear $\mathcal{O}(M)$ run-time. With the help of new tensorial objects called energy flow moments, we achieve a fast implementation of jet substructure observables like $C_2$ and $D_2$, which are widely used at the Large Hadron Collider to identify boosted hadronic resonances. As another application, we compute the number of leafless multigraphs with $d$ edges up to $d=16(15,641,159)$, conjecturing that this is the same as the number of independent kinematic polynomials of degree $d$, previously known only to $d=8$ (279).

We find the exchange symmetry between left and right handed top quark in composite Higgs model with partial compositeness is efficient to soften the Higgs potential and reduce fine tuning. This symmetry can keep the Higgs potential in top sector invariant under trigonometric parity $\sin (h/f)\leftrightarrow \cos (h/f)$. Thus the Higgs quadratic divergences can be canceled entirely, resulting in a UV insensitive Higgs potential. We explicitly construct the minimal left-right symmetric model based on coset space $SO(6)/SO(5)$, which is locally isomorphic to $SU(4)/Sp(4)$ and thus has well defined fermionic UV completion. This UV completion can automatically keep Higgs potential in the gauge sector finite even the gauge sector breaks this discrete symmetry. We find that the vector mesons can be very heavy, while the colored top partners are relatively light ($>1.5\mathrm{TeV}$) to obtain a light Higgs.

The constraints on nonminimal dark sectors involving ensembles of unstable dark-matter species are well established and quite stringent in cases in which these species decay to visible-sector particles. However, in cases in which these ensembles decay exclusively to other, lighter dark-sector states, the corresponding constraints are less well established. In this paper, we investigate how information about the expansion rate of the universe at low redshifts gleaned from observations of Type Ia supernovae can be used to constrain ensembles of unstable particles which decay primarily into dark radiation.

Lattice gauge theories form a very successful framework for studying nonperturbative gauge field physics, in particular in quantum chromodynamics. Recently, their quantum simulation on atomic and solid-state platforms has been discussed, aiming at overcoming some of the difficulties still faced by the conventional approaches (such as the sign problem and real time evolution). While the actual implementations of a lattice gauge theory on a quantum simulator may differ in terms of the simulating system and its properties, they are all directed at studying similar physical phenomena, requiring the measurement of nonlocal observables, due to the local symmetry of gauge theories. In this work, general schemes for measuring such nonlocal observables (Wilson loops and mesonic string operators) in general lattice gauge theory quantum simulators that are based merely on local operations are proposed.

Mixing in the ${\mathrm{\Sigma }}^0$–${\mathrm{\Lambda }}^0$ system is a direct consequence of broken isospin symmetry and is a measure of both isospin-symmetry breaking as well as general SU(3)-flavor symmetry breaking. In this work we present a new scheme for calculating the extent of ${\mathrm{\Sigma }}^0$–${\mathrm{\Lambda }}^0$ mixing using simulations in lattice $\mathrm{QCD}+\mathrm{QED}$ and perform several extrapolations that compare well with various past determinations. Our scheme allows us to easily contrast the QCD-only mixing case with the full $\mathrm{QCD}+\mathrm{QED}$ mixing.

There have been rapid developments in the direct calculation in lattice QCD (LQCD) of the Bjorken-$x$ dependence of hadron structure through large-momentum effective theory (LaMET). LaMET overcomes the previous limitation of LQCD to moments (that is, integrals over Bjorken $x$) of hadron structure, allowing LQCD to directly provide the kinematic regions where the experimental values are least known. LaMET requires large-momentum hadron states to minimize its systematics and allow us to reach small-$x$ reliably. This means that very fine lattice spacing to minimize lattice artifacts at order $(P_{z}a{)}^n$ will become crucial for next-generation LaMET-like structure calculations. Furthermore, such calculations require operators with long Wilson-link displacements, especially in finer lattice units, increasing the communication costs relative to that of the propagator inversion. In this work, we explore whether machine-learning algorithms can make predictions of correlators to reduce the computational cost of these LQCD calculations. We consider two algorithms, gradient-boosting decision tree and linear models, applied to LaMET data, the matrix elements needed to determine the kaon and ${\eta }_s$ unpolarized parton distribution functions (PDFs), meson distribution amplitude (DA), and the nucleon gluon PDF. We find that both algorithms can reliably predict the target observables with different prediction accuracy and systematic errors. The predictions from smaller displacement $z$ to larger ones work better than those for momentum $p$ due to the higher correlation among the data.

The RQCD Collaboration proposed a projection method to remove the excited-state contamination in lattice QCD calculations of nuclear form factors. The effectiveness of this method in removing the two-particle nucleon-pion-state contamination is examined using chiral perturbation theory. It is shown that the projection method has practically no impact in the calculation of the axial and induced pseudoscalar form factors. In the pseudoscalar form factor the projection method strongly enhances the nucleon-pion-state contamination. The generalized Goldberger-Treiman relation is satisfied even though large nucleon-pion-state contaminations are present in individual form factors. Therefore, the projection method is not a solution to the excited-state problem in nucleon form factor calculations.

We study exclusive quarkonium production in the dipole picture at next-to-leading-order (NLO) accuracy, using the nonrelativistic expansion for the quarkonium wave function. This process offers one of the best ways to obtain information about gluon distributions at small $x$, in ultraperipheral heavy ion collisions and in deep inelastic scattering. The quarkonium light-cone wave functions needed in the dipole picture have typically been available only at tree level, either in phenomenological models or in the nonrelativistic limit. In this paper, we discuss the compatibility of the dipole approach and the nonrelativistic expansion and compute NLO relativistic corrections to the quarkonium light-cone wave function in light-cone gauge. Using these corrections, we recover results for the NLO decay width of quarkonium to $e^{+}{e}^{-}$, and we check that the nonrelativistic expansion is consistent with Efremov-Radyushkin-Brodsky-Lepage evolution and with Balitsky-Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner evolution of the target. The results presented here will allow computing the exclusive quarkonium production rate at NLO once the one-loop photon wave function with massive quarks, currently under investigation, is known.

In this paper, we calculate the total decay widths for the $W^{+}$-boson decays, $W^{+}\to B_c+b+\overline{s}+X$ and $W^{+}\to B_c^{*}+b+\overline{s}+X$, up to next-to-leading order (NLO) accuracy within the framework of the nonrelativistic QCD theory. Both the fixed-order and the fragmentation approaches are adopted to do the calculation. Differential decay widths $d\mathrm{\Gamma }/dz$ and $d\mathrm{\Gamma }/d{s}_1$ are also given. We find that the NLO corrections are significant in those two $W^{+}$ decay channels. Our numerical results show that at the LHC, there are about $7.03\times {10}^4$ $B_c$-meson events and $5.10\times {10}^4$ $B_c^{*}$-meson events to be produced via the $W^{+}$-boson decays per operation year.