Using N-body simulations, we measure the power spectrum of the effective dark matter density field, which is defined through the modified Poisson equation in $f(R)$ cosmologies. We find that, when compared to the conventional dark matter power spectrum, the effective power spectrum deviates more significantly from the $\mathrm{\Lambda }\mathrm{CDM}$ model. For models with $f_{R0}=-10^{-4}$, the deviation can exceed 150%, while the deviation of the conventional matter power spectrum is less than 50%. Even for models with $f_{R0}=-10^{-6}$, for which the conventional matter power spectrum is very close to the $\mathrm{\Lambda }\mathrm{CDM}$ prediction, the effective power spectrum shows sizeable deviations. Our results indicate that traditional analyses based on the dark matter density field may seriously underestimate the impact of $f(R)$ gravity on galaxy clustering. We therefore suggest the use of the effective density field in such studies. In addition, based on our findings, we also discuss several possible methods of making use of the differences between the conventional and effective dark matter power spectra in $f(R)$ gravity to discriminate the theory from the $\mathrm{\Lambda }\mathrm{CDM}$ model.

We consider a phenomenological model of inflation where the inflaton is the phase of a complex scalar field $\mathrm{\Phi }$. Planck-suppressed operators of $\mathcal{O}(f^5/M_{\mathrm{pl}})$ modify the geometry of the vev $⟨\mathrm{\Phi }⟩$ at first order in the decay constant $f$, which adds a first-order periodic term to the definition of the canonically normalized inflaton $\varphi$. This correction to the inflaton induces a fixed number of extra oscillatory terms in the potential $V\sim {\theta }^p$. We derive the same result in a toy scenario where the vacuum $⟨\mathrm{\Phi }⟩$ is an ellipse with an arbitrarily large eccentricity. These extra oscillations change the form of the power spectrum as a function of scale $k$ and provide a possible mechanism for differentiating effective field theory motivated inflation from models where the angular shift symmetry is a gauge symmetry.

We determine the large-distance behavior of the static dipole-dipole potential for a wide class of gauge theories on nonperturbative grounds, exploiting only general properties of the theory. In the case of QCD, we recover the known results in the regime of small dipole sizes and discuss recent nonperturbative calculations. Moreover, we discuss the case of pure-gauge theories and compare our prediction with the available lattice results.

In [Phys. Rev. Lett. 114, 061601 (2015)], we reported on a new universality class for longitudinally expanding systems, encompassing strongly correlated non-Abelian plasmas and $N$-component self-interacting scalar field theories. Using classical-statistical methods, we showed that these systems share the same self-similar scaling properties for a wide range of momenta in a limit where particles are weakly coupled but their occupancy is high. Here we significantly expand on our previous work and delineate two further self-similar regimes. One of these occurs in the deep infrared (IR) regime of very high occupancies, where the nonequilibrium dynamics leads to the formation of a Bose-Einstein condensate. The universal IR scaling exponents and the spectral index characterizing the isotropic IR distributions are described by an effective theory derived from a systematic large-$N$ expansion at next-to-leading order. Remarkably, this effective theory can be cast as a vertex-resummed kinetic theory. The other novel self-similar regime occurs close to the hard physical scale of the theory, and sets in only at later times. We argue that the important role of the infrared dynamics ensures that key features of our results for scalar and gauge theories cannot be reproduced consistently in conventional kinetic theory frameworks.

A feasibility study is presented for the search of the lightest bottom squark (sbottom) in a compressed scenario, where its mass difference from the lightest neutralino is 5 GeV. Two separate studies are performed: 1) a final state containing two vector-boson-fusion (VBF)-like tagged jets, missing transverse energy, and zero or one $b$-tagged jet; and 2) a final state consisting of an initial state radiation jet, missing transverse energy, and at least one $b$-tagged jet. An analysis of the shape of the missing transverse energy distribution for signal and background is performed in each case, leading to significant improvement over a cut and count analysis, especially after incorporating the consideration of systematic uncertainty and pileup. The shape analysis in the VBF-like tagged jet study leads to a $3\sigma$ exclusion potential of sbottoms with mass up to 530(462) GeV for an integrated luminosity of $300{\mathrm{fb}}^{-1}$ at 14 TeV, with 5% systematic uncertainty and $\mathrm{PU}=0(50)$.

We calculate Higgs decay rates into $\gamma \gamma$ and $Z\gamma$ in the minimal supersymmetric Standard Model and ($B\text{−}L$) supersymmetric Standard Model by allowing for contributions from light staus ($\tilde{\tau }\mathrm{s}$) and charginos (${\tilde{\chi }}^{\pm }\mathrm{s}$). We show that sizable departures are possible from the Standard Model predictions for the 125 GeV state and that they are testable during Run 2 at the Large Hadron Collider. Furthermore, we illustrate how a second light scalar Higgs signal in either or both of these decay modes can be accessed at the CERN machine rather promptly within the ($B\text{−}L$) supersymmetric Standard Model, a possibility instead precluded to the minimal supersymmetric Standard Model, owing to the much larger mass of its heavy scalar state.

Light gauge bosons can lead to resonant interactions between high-energy astrophysical neutrinos and the cosmic neutrino background. We study this possibility in detail, considering the ability of IceCube to probe such scenarios. We find the most dramatic effects in models with a very light $Z^{\prime }$ ($m_{Z^{\prime }}\lesssim 10\mathrm{MeV}$), which can induce a significant absorption feature at $E_{\nu }\sim 5–10\mathrm{TeV}\times (m_{Z^{\prime }}/\mathrm{MeV}{)}^2$. In the case of the inverted hierarchy and a small sum of neutrino masses, such a light $Z^{\prime }$ can result in a broad and deep spectral feature at $\sim 0.1–10\mathrm{PeV}\times (m_{Z^{\prime }}/\mathrm{MeV}{)}^2$. Current IceCube data already excludes this case for a $Z^{\prime }$ lighter than a few MeV and couplings greater than $g\sim 10^{-4}$. We emphasize that the ratio of neutrino flavors observed by IceCube can be used to further increase their sensitivity to $Z^{\prime }$ models and to other exotic physics scenarios.

We explore the scenarios where the only accessible new states at the electroweak scale consist of a pair of color-singlet electroweak particles, the masses of which are degenerate at the tree level and split only by electroweak symmetry breaking at the loop level. For the sake of illustration, we consider a supersymmetric model and study the following three representative cases with the lower-lying states as (a) two spin-$1/2$ Higgsino ${\mathrm{SU}(2)}_L$ doublets, (b) a spin-$1/2$ wino ${\mathrm{SU}(2)}_L$ triplet and (c) a spin-0 left-handed slepton ${\mathrm{SU}(2)}_L$ doublet. Due to the mass degeneracy, those lower-lying electroweak states are difficult to observe at the LHC and rather challenging to detect at the $e^{+}{e}^{-}$ collider as well. We exploit the pair production in association with a hard photon radiation in high energy $e^{+}{e}^{-}$ collisions. If kinematically accessible, such single-photon processes at $e^{+}{e}^{-}$ colliders with polarized beams enable us to characterize each scenario by measuring the energy of the associated hard photon and to determine the spin of the nearly invisible particles unambiguously through the threshold behavior in the photon energy distribution.

We calculate the bound state properties of stoponium using lattice formulation of nonrelativistic effective field theory for stop which is moving nonrelativistically in the rest frame of stoponium. Our calculation method is similar to that employed in lattice nonrelativistic quantum chromodynamics (NRQCD) studies for charmonium and bottomonium. Using ${16}^3\times 256$ quenched lattice gauge field configurations at $a^{-1}=50(1)\mathrm{GeV}$, we obtain the stoponium mass and the lattice matrix element which is related to the wave function at the origin for the $1S$ state and find that the lattice $|R_{1S}(0){|}^2/M_{1S}^3$ is 3.5–4 larger than that from a potential model calculation for $200\mathrm{GeV}\le M_{1S}\le 800\mathrm{GeV}$.

We investigate the transverse polarization of a hyperon produced in the high-energy unpolarized proton-proton collision, $pp\to {\mathrm{\Lambda }}^{\uparrow }X$, based on the collinear twist-3 factorization formalism. We focus on the contribution from the twist-3 distribution in one of the unpolarized proton and the transversity fragmentation function for the final hyperon. Utilizing the “master formula” for the soft-gluon-pole cross section, we clarify the reason for why it receives only the derivative term of the twist-3 distribution. We also present the first computation of the soft-fermion-pole cross section and found that it vanishes. This means that the derivative of the soft-gluon-pole function is the only source for the twist-3 cross section from the unpolarized twist-3 distribution, which provides a useful basis for a phenomenological analysis.

We present a series of observables for soft inclusive physics, and utilize them for comparison between two recently developed color reconnection models: the new color reconnection model in pythia and the DIPSY rope hadronization model. The observables are ratios of identified hadron yields as a function of the final-state activity, as measured by the charged multiplicity. Since both considered models have a nontrivial dependence on the final-state activity, the above observables serve as excellent probes to test the effect of these models. Both models show a clear baryon enhancement with increasing multiplicity, while only the DIPSY rope model leads to a strangeness enhancement. Flowlike patterns, previously found to be connected to color reconnection models, are investigated for the new models. Only pythia shows a $p_{\perp }$-dependent enhancement of the $\mathrm{\Lambda }/K$ ratio as the final-state activity increases, with the enhancement being largest in the mid-$p_{\perp }$ region.

We put forward a functional renormalization group approach for the direct computation of real time correlation functions, also applicable at finite temperature and density. We construct a general class of regulators that preserve the space-time symmetries, and allows the computation of correlation functions at complex frequencies. This includes both imaginary time and real time, and allows in particular the use of the plethora of imaginary time results for the computation of real time correlation functions. We also discuss real time computation on the Keldysh contour with general spatial momentum regulators. Both setups give access to the general momentum and frequency dependence of correlation functions.

Theoretical estimates for the half-life of neutrinoless double beta decay ($0\nu \beta \beta$) in candidate nuclei are affected by both particle and nuclear physics uncertainties, which may complicate the interpretation of decay signals or limits. We study such uncertainties and their degeneracies in the following context: three $0\nu \beta \beta$ nuclei of great interest for large-scale experiments (${}^{76}\mathrm{Ge}$, ${}^{130}\mathrm{Te}$, ${}^{136}\mathrm{Xe}$), two representative particle physics mechanisms (light and heavy Majorana neutrino exchange), and a large set of nuclear matrix elements (NME), computed within the quasiparticle random phase approximation (QRPA). It turns out that the main theoretical uncertainties, associated with the effective axial coupling $g_A$ and with the nucleon-nucleon potential, can be parametrized in terms of NME rescaling factors, up to small residuals. From this parametrization, the following QRPA features emerge: (1) the NME dependence on $g_A$ is milder than quadratic, (2) in each of the two mechanisms, the relevant lepton number violating parameter is largely degenerate with the NME rescaling factors, and (3) the light and heavy neutrino exchange mechanisms are basically degenerate in the above three nuclei. We comment on the challenging theoretical and experimental improvements required to reduce such particle and nuclear physics uncertainties and their degeneracies.

Searches for both resonant and nonresonant Higgs boson pair production are performed in the $hh\to bb\tau \tau$, $\gamma \gamma W{W}^{*}$ final states using $20.3{\mathrm{fb}}^{-1}$ of $pp$ collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95% confidence-level upper limits on the production cross sections are set. These results are then combined with the published results of the $hh\to \gamma \gamma bb$, $bbbb$ analyses. An upper limit of 0.69 (0.47) pb on the nonresonant $hh$ production is observed (expected), corresponding to 70 (48) times the SM $gg\to hh$ cross section. For production via narrow resonances, cross-section limits of $hh$ production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. These results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model.

A meaningful probability distribution for measurements of a quantum stress tensor operator can only be obtained if the operator is averaged in time or in spacetime. This averaging can be regarded as a description of the measurement process. Realistic measurements can be expected to begin and end at finite times, which means that they are described by functions with compact support, which we will also take to be smooth. Here we study the probability distributions for stress tensor operators averaged with such functions of time, in the vacuum state of a massless free field. Our primary aim is to understand the asymptotic form of the distribution which describes the probability of large vacuum fluctuations. Our approach involves asymptotic estimates for the high moments of the distribution. These estimates in turn may be used to obtain estimates for the asymptotic form of the probability distribution. Our results show that averaging over a finite interval results in a probability distribution which falls more slowly than for the case of Lorentzian averaging, and both fall more slowly than exponentially. This indicates that vacuum fluctuations effects can dominate over thermal fluctuations in some circumstances.

In three dimensions, every known $\mathcal{N}=4$ supermultiplet has an off-shell completion. However, there is no off-shell $\mathcal{N}=4$ formulation for the known extended superconformal Chern-Simons (CS) theories with eight and more supercharges. To achieve a better understanding of this issue, we provide $\mathcal{N}=4$ superfield realizations for the equations of motion which correspond to various $\mathcal{N}=4$ and $\mathcal{N}=6$ superconformal CS theories, including the Gaiotto-Witten theory and the Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. These superfield realizations demonstrate that the superconformal CS theories with $\mathcal{N}\ge 4$ (except for the Gaiotto-Witten theory) require a reducible long $\mathcal{N}=4$ vector multiplet, from which the standard left and right $\mathcal{N}=4$ vector multiplets are obtained by constraining the field strength to be either self-dual or antiself-dual. Such a long multiplet naturally originates upon reduction of any off-shell $\mathcal{N}>4$ vector multiplet to $\mathcal{N}=4$ superspace. For the long $\mathcal{N}=4$ vector multiplet we develop a prepotential formulation. It makes use of two prepotentials being subject to the constraint which defines the so-called hybrid projective multiplets introduced in the framework of $\mathcal{N}=4$ supergravity-matter systems in arXiv:1101.4013. We also couple $\mathcal{N}=4$ superconformal CS theories to $\mathcal{N}=4$ conformal supergravity.

We construct Kundt solutions of minimal massive gravity theory and show that, similar to topologically massive gravity (TMG), most of them are constant scalar invariant (CSI) spacetimes that correspond to deformations of round and warped (A)dS. We also find an explicit non-CSI Kundt solution at the merger point. Finally, we give their algebraic classification with respect to the traceless Ricci tensor (Segre classification) and show that their Segre types match with the types of their counterparts in TMG.

We construct an $n$-dimensional Born–Infeld-type gravity theory that has the same properties as Einstein’s gravity in terms of the vacuum and particle content: Namely, the theory has a unique viable vacuum (maximally symmetric solution) and a single massless unitary spin-2 graviton about this vacuum. The Born–Infeld gravity, in some sense, is the most natural, minimal generalization of Einstein’s gravity with a better UV behavior and hence is a potentially less singular theory at small distances. The Gauss–Bonnet combination plays a nontrivial role in the construction of the theory. As an extreme example, we consider the infinite-dimensional limit where an interesting exponential gravity arises.

We argue that the exponential relation $g_{\mu \nu }={\overline{g}}_{\mu \rho }({\mathrm{e}}^h{{)}^{\rho }}_{\nu }$ is the most natural metric parametrization since it describes geodesics that follow from the basic structure of the space of metrics. The corresponding connection is derived, and its relation to the Levi-Civita connection and the Vilkovisky–DeWitt connection is discussed. We address the impact of this geometric formalism on quantum gravity applications. In particular, the exponential parametrization is appropriate for constructing covariant quantities like a reparametrization-invariant effective action in a straightforward way. Furthermore, we reveal an important difference between Euclidean and Lorentzian signatures: Based on the derived connection, any two Euclidean metrics can be connected by a geodesic, while this does not hold for the Lorentzian case.

This paper is devoted to showing that the bosonic sector of ${\mathcal{R}}^2$ supergravity in four dimensions, constructed with the $F$ term, admits a variety of exact and analytic solutions which include pp and anti–de Sitter (AdS) waves, asymptotically flat and AdS black holes and wormholes, as well as product spacetimes. The existence of static black holes and wormholes implies that a combination involving the Ricci scalar plus the norm of the field strength of the auxiliary two-form $B_{\mu \nu }$ must be a constant. We focus on this sector of the theory, which has two subsectors depending on whether such a combination vanishes.