We obtain the partial-wave unitarity constraints on the lowest-dimension effective operators which generate anomalous quartic gauge couplings but leave the triple gauge couplings unaffected. We consider operator expansions with linear and nonlinear realizations of the electroweak symmetry and explore the multidimensional parameter space of the coefficients of the relevant operators: 18 dimension-eight operators in the linear expansion and 5 $\mathcal{O}(p^4)$ operators in the derivative expansion. We study two-to-two scattering of electroweak gauge bosons and Higgs bosons, taking into account all coupled channels and all possible helicity amplitudes for the $J=0$, 1 partial waves. In general, the bounds degrade by factors of a few when several operator coefficients are considered to be nonvanishing simultaneously. However, this requires considering constraints from both $J=0$ and $J=1$ partial waves for some sets of operators.

At large values of $x$, the parton distribution functions (PDFs) of the proton are poorly constrained and there are considerable variations between different global fits. Data at such high $x$ have already been published by the ZEUS Collaboration, but not yet used in PDF extractions. A technique for comparing predictions based on different PDF sets to the observed number of events in the ZEUS data is presented. It is applied to compare predictions from the most commonly used PDFs to published ZEUS data at high Bjorken $x$. A wide variation is found in the ability of the PDFs to predict the observed results. A scheme for including the ZEUS high-$x$ data in future PDF extractions is discussed.

We study a large class of supersymmetric solutions in four-dimensional $N=5$ gauged supergravity with the $SO(5)$ gauge group. There is only one $N=5$ supersymmetric ${\mathrm{AdS}}_4$ vacuum preserving the full $SO(5)$ symmetry dual to an $N=5$ superconformal field theory (SCFT) in three dimensions. We give a number of domain walls interpolating between this ${\mathrm{AdS}}_4$ fixed point and singular geometries in the IR with $SO(4)$ and $SO(3)$ symmetries. These solutions describe RG flows from the $N=5$ SCFT to nonconformal field theories driven by mass deformations. The $SO(4)$ solutions are precisely in agreement with the previously known mass deformations within the dual $N=5$ SCFT. We also find supersymmetric Janus solutions describing two-dimensional conformal defects in the $N=5$ SCFT with $N=(4,1)$ and $N=(1,1)$ supersymmetries on the defects. Finally, we study supersymmetric solutions of the form ${\mathrm{AdS}}_2\times {\mathrm{\Sigma }}^2$, with ${\mathrm{\Sigma }}^2=S^2,H^2$ being a Riemann surface, corresponding to near horizon geometries of ${\mathrm{AdS}}_4$ black holes. We consider both magnetic and dyonic solutions and find that there exists a class of magnetic ${\mathrm{AdS}}_2\times H^2$ solutions with $SO(2)$ symmetry. It is rather remarkable that a complete analytic solution interpolating between ${\mathrm{AdS}}_4$ and ${\mathrm{AdS}}_2\times H^2$ with a running scalar can be obtained. The solution corresponds to a twisted compactification of $N=5$ SCFT to superconformal quantum mechanics. We also show that no purely magnetic or dyonic black holes with ${\mathrm{AdS}}_2\times {\mathrm{\Sigma }}^2$ horizon from $SO(2)\times SO(2)$ twist exist in $N=5$, $SO(5)$ gauged supergravity.

We study the geometry and mechanics (both classical and quantum) of potential wells described by squares of Chebyshev polynomials. We show that in a small neighborhood of the locus cut out by them in the space of hyperelliptic curves, these systems exhibit low-orders/low-orders resurgence, where perturbative fluctuations about the vacuum determine perturbative fluctuations about nonperturbative saddles.

The Hadamard renormalization procedure is applied to a free, massive Dirac field $\psi$ on a two-dimensional Lorentzian spacetime. This yields the state-independent divergent terms in the Hadamard bispinor $G^{(1)}(x,x^{\prime })=\frac{1}{2}⟨[\overline{\psi }(x^{\prime }),\psi (x)]⟩$ as $x$ and $x^{\prime }$ are brought together along the unique geodesic connecting them. Subtracting these divergent terms within the limit assigns $G^{(1)}(x,x^{\prime })$, and thus any operator expressed in terms of it, a finite value at the coincident point $x^{\prime }=x$. In this limit, one obtains a quadratic operator instead of a bispinor. The procedure is thus used to assign finite values to various quadratic operators, including the stress-energy tensor. Results are presented covariantly, in a conformally flat coordinate chart at purely spatial separations, and in the Minkowski metric. These terms can be directly subtracted from combinations of $G^{(1)}(x,x^{\prime })$—themselves obtained, for example, from a numerical simulation—to obtain finite expectation values defined in the continuum.

We present a model for the coupling of nonrelativistic quantum systems with a linearized gravitational field from a Lagrangian formulation. The coupling strongly resembles the light-matter interaction models that are known to be well approximated by the Unruh-DeWitt detector model for interactions with quantum fields. We then apply our model to linearized quantum gravity, which allows us to propose a detector based setup that can in principle probe the quantum nature of the gravitational field.

We study a field-theoretic model with an eighth-degree polynomial potential—the ${\phi }^8$ model. We show that for some certain ratios of constants of the potential, the problem of finding kink-type solutions in ($1+1$)-dimensional space-time reduces to solving algebraic equations. For two different ratios of the constants, which determine positions of the vacua, we obtained explicit formulas for kinks in all topological sectors. The properties of the obtained kinks are also studied—their masses are calculated, and the excitation spectra which could be responsible for the appearance of resonance phenomena in kink-antikink scattering are found.

This article investigates the properties of a scalar fifth force that arises in a scalar tensor-theory with a chameleon screening mechanism in the context of gravity space missions like the MICROSCOPE experiment. In such an experiment, the propagation of the chameleon field inside the nested cylinders of the experiment causes a fifth force when the cylinders are not perfectly coaxial. We propose a semianalytic method to compute the field distribution and the induced fifth force and compare it to a full numerical simulation, in settings where the cylindrical symmetry is broken. The scaling of the fifth force with both the parameters of the model and the geometry of the experiment is discussed. We show that the fifth force is repulsive, hence adds a destabilizing stiffness that should be included in the force budget acting on the detector. This opens the way to a new method to constrain a scalar fifth force in screened models.

Scalar Gauss-Bonnet gravity is the only theory with quadratic curvature corrections to general relativity whose field equations are of second differential order. This theory allows for nonperturbative dynamical corrections and is therefore one of the most compelling case studies for beyond-general relativity effects in the strong-curvature regime. However, having second-order field equations is not a guarantee for a healthy time evolution in generic configurations. As a first step toward evolving black-hole binaries in this theory, we here derive the $3+1$ decomposition of the field equations for any (not necessarily small) coupling constant, and we discuss potential challenges of its implementation.

Over the past year, a handful of new gravitational wave models have been developed to include multiple harmonic modes thereby enabling for the first time fully Bayesian inference studies including higher modes to be performed. Using one recently developed numerical relativity surrogate model, NRHybSur3dq8, we investigate the importance of higher modes on parameter inference of coalescing massive binary black holes. We focus on examples relevant to the current three-detector network of observatories, with a detector-frame mass set to $120M_{\odot }$ and with signal amplitude values that are consistent with plausible candidates for the next few observing runs. We show that for such systems the higher mode content will be important for interpreting coalescing binary black holes, reducing systematic bias, and computing properties of the remnant object. Even for comparable-mass binaries and at low signal amplitude, the omission of higher modes can influence posterior probability distributions. We discuss the impact of our results on source population inference and self-consistency tests of general relativity. Our work can be used to better understand asymmetric binary black hole merger events, such as GW190412. Higher modes are critical for such systems, and their omission usually produces substantial parameter biases.

Trapped regions bounded by horizons are the defining features of black holes. However, formation of a singularity-free apparent horizon in finite time of a distant observer is consistent only with special states of geometry and matter in its vicinity. In spherical symmetry such horizons exist only in two classes of solutions of the Einstein equations. Both violate the null energy condition (NEC) and allow for expanding and contracting trapped regions. However, an expanding trapped region leads to a firewall. The weighted time average of the energy density for an observer crossing this firewall is negative and exceeds the maximal NEC violation that quantum fields can produce. As a result, either black holes can only evaporate or the semiclassical physics breaks down already at the horizons. Geometry of a contracting trapped region approaches the ingoing Vaidya metric with decreasing mass. Only one class of solutions allows for a test particle to cross the apparent horizon, and for a thin shell to collapse into a black hole. These results significantly constrain the regular black hole models. Models with regular matter properties at the horizon can be realized only if significant departures from the semiclassical physics occur already at the horizon scale. The Hayward-Frolov model may describe only evaporation, but not formation of a regular black hole.

Advanced gravitational-wave detectors are limited by quantum noise in their most sensitive frequency band. Quantum noise suppression techniques, such as the application of the quantum squeezed state of light, have been actively studied in the context of homodyne readouts. In this paper, we consider quantum squeezing schemes for the heterodyne readouts. This is motivated by a successful suppression of the higher-order-mode content by stable recycling cavities in advanced detectors. The heterodyne readout scheme requires precise tuning of the interferometer parameters and a broadband squeezing source, but is conceptually simple and elegant. We further show that it is compatible with the frequency-dependent squeezing, which reduces both the shot noise and the radiation-pressure noise. We propose a test of the heterodyne readout with squeezing in Advanced LIGO. This can serve as a pathfinder not only for the implementation in future detectors, such as the Einstein Telescope and Cosmic Explorer, but also for general high-precision optical measurements.

We derive a Hamiltonian formulation of the theory of gauge invariant, linear perturbations in anisotropic Bianchi I spacetimes, and describe how to quantize this system. The matter content is assumed to be a minimally coupled scalar field with potential $V(\varphi )$. We show that a Bianchi I spacetime generically induces both anisotropies and quantum entanglement on cosmological perturbations, and provide the tools to compute the details of these features. We then apply this formalism to a scenario in which the inflationary era is preceded by an anisotropic Bianchi I phase, and discuss the potential imprints in observable quantities. The formalism developed here paves the road to a simultaneous canonical quantization of both the homogeneous degrees of freedom and the perturbations, a task that we develop in a companion paper.

In this work we show how the criterion of asymptotic Hamiltonian diagonalization originated in hybrid quantum cosmology serves to pick out a unique vacuum for the Dirac field in de Sitter, in the context of quantum field theory in curved spacetimes. This criterion is based on the dynamical definition of annihilation and creationlike variables for the fermionic field, which obey the linearized dynamics of a Hamiltonian that has been diagonalized in a way that is adapted to its local spatial structure. This leads to fermionic variables that possess a precise asymptotic expansion in the ultraviolet limit of large wave numbers. We explicitly show that, when the cosmological background is fixed as a de Sitter solution, this expansion uniquely selects the choice of fermionic annihilation and creationlike variables for all spatial scales, and thus picks out a unique privileged Fock representation and vacuum state for the Dirac field in de Sitter. The explicit form of the basis of solutions to the Dirac equation associated with this vacuum is then computed.

The transverse momentum-dependent (TMD) and collinear higher twist theoretical factorization frameworks are the most frequently used approaches to describe spin-dependent hard cross sections weighted by and integrated over transverse momentum. Of particular interest is the contribution from small transverse momentum associated with the target bound state. In phenomenological applications, this contribution is often investigated using transverse momentum weighted integrals that sharply regulate the large transverse momentum contribution, for example, with Gaussian parametrizations. Since the result is a kind of hybrid of TMD and collinear (inclusive) treatments, it is important to establish if and how the formalisms are related in applications to weighted integral observables. The suppression of a large transverse momentum tail, for example, can potentially affect the type of evolution that is applicable. We find that a naive version of a widely used identity relating the $k_T^2$-weighted and integrated Sivers TMD function to a renormalized twist-3 function has strongly ambiguous ultraviolet contributions, and that corrections to it are not necessarily perturbatively suppressed. We discuss the implications for applications, arguing in particular that the relevant evolution for transverse momentum weighted and integrated cross sections with sharp effective large transverse momentum cutoffs is of the TMD form rather than the standard renormalization group evolution of collinear correlation functions.

Light new physics weakly coupled to the Higgs can induce a strong first-order electroweak phase transition (EWPT). Here, we argue that scenarios in which the EWPT is driven first-order by a light scalar with mass between $\sim 10\mathrm{GeV}-m_h/2$ and small mixing with the Higgs will be conclusively probed by the high-luminosity LHC and future Higgs factories. Our arguments are based on analytic and numerical studies of the finite-temperature effective potential and provide a well-motivated target for exotic Higgs decay searches at the LHC and future lepton colliders.

We revisit the scalar singlet dark matter (DM) scenario with a pair of dark lepton partners which form a vectorlike Dirac fermionic doublet. The extra doublet couples with the Standard Model (SM) leptonic doublet and the scalar singlet via a non-SM-like Yukawa structure. As a result, (i) since the extra fermionic states interact with other dark sector particles as well as the SM via gauge and Yukawa interactions, it gives rise to new DM annihilation processes including pair annihilation as well as coannihilation channels, and (ii) such a Yukawa structure opens up new production channels for leptonic final states giving much enhancement in cross sections to search for dark matter in the LHC. Using suitable kinematic observables, we train a boosted decision tree classifier to separate enhanced but still feeble light leptonic signals from the background in an effective manner. On the other hand, the same technique is applied to study $\tau$-tagged jets in the search for DM signals.

I present a calculation of the topological susceptibility ${\chi }_T$ in $SU(N_c)$ gauge theory with $N_c=3–5$ colors and $N_f=2$ degenerate flavors of fermions. The results lie on a common curve when expressed in terms of the combination $N_c{m}_{PS}^2{t}_0$ where $m_{PS}$ is the pseudoscalar meson mass and $t_0$ is the flow parameter. ${\chi }_T$ approaches its quenched value as the pseudoscalar mass becomes large. The lattice simulations use clover fermions. They are done at a single lattice spacing, roughly matched across $N_c$, and over a restricted range of fermion masses.

Based on the observation that the heavy quark–antiquark potential value at infinity corresponds to twice the $D$ meson mass, we constrain the asymptotic value of the heavy quark potential in a hot medium through a QCD sum rule calculation of the $D$ meson at finite temperature. We find that to correctly reproduce the QCD sum rule results as well as a recent model calculation for the $D$ meson mass near the critical temperature, the heavy quark potential should be composed mostly of the free energy with an addition of a small but nontrivial fraction of the internal energy. Combined with a previous study comparing potential model results for the $J/\psi$ to a QCD sum rule calculation, we conclude that the composition of the effective heavy quark potential should depend on the interquark distance. Namely, the potential is dominated by the free energy at short distance, while at larger separation, it has a fraction of about 20% of internal energy.