We analyze the parametric structure of twin Higgs (TH) theories and assess the gain in fine tuning which they enable compared to extensions of the standard model with colored top partners. Estimates show that, at least in the simplest realizations of the TH idea, the separation between the mass of new colored particles and the electroweak scale is controlled by the coupling strength of the underlying UV theory, and that a parametric gain is achieved only for strongly-coupled dynamics. Motivated by this consideration we focus on one of these simple realizations, namely composite TH theories, and study how well such constructions can reproduce electroweak precision data. The most important effect of the twin states is found to be the infrared contribution to the Higgs quartic coupling, while direct corrections to electroweak observables are subleading and negligible. We perform a careful fit to the electroweak data including the leading-logarithmic corrections to the Higgs quartic up to three loops. Our analysis shows that agreement with electroweak precision tests can be achieved with only a moderate amount of tuning, in the range 5%–10%, in theories where colored states have mass of order 3–5 TeV and are thus out of reach of the LHC. For these levels of tuning, larger masses are excluded by a perturbativity bound, which makes these theories possibly discoverable, hence falsifiable, at a future 100 TeV collider.

We consider the dark matter (DM) scenario in the context of the classically conformal ${\mathrm{U}(1)}^{\prime }$ extended standard model (SM), with three right-handed neutrinos (RHNs) and the ${\mathrm{U}(1)}^{\prime }$ Higgs field. The model is free from all of the ${\mathrm{U}(1)}^{\prime }$ gauge and gravitational anomalies in the presence of the three RHNs. We introduce a $Z_2$ parity in the model, under which an odd parity is assigned to one RHN, while all of the other particles are assigned to be $Z_2$ even, and hence the $Z_2$-odd RHN serves as a DM candidate. In this model, the ${\mathrm{U}(1)}^{\prime }$ gauge symmetry is radiatively broken through the Coleman-Weinberg mechanism, by which the electroweak symmetry breaking is triggered. There are three free parameters in our model—the ${\mathrm{U}(1)}^{\prime }$ charge of the SM Higgs doublet ($x_H$), the new ${\mathrm{U}(1)}^{\prime }$ gauge coupling ($g_X$), and the ${\mathrm{U}(1)}^{\prime }$ gauge boson ($Z^{\prime }$) mass ($m_{Z^{\prime }}$)—which are severely constrained in order to solve the electroweak vacuum instability problem, and satisfy the LHC Run-2 bounds from the search for the $Z^{\prime }$ boson resonance. In addition to these constraints, we investigate the RHN DM physics. Because of the nature of classical conformality, we find that a RHN DM pair mainly annihilates into the SM particles through $Z^{\prime }$ boson exchange. This is the so-called $Z^{\prime }$-portal DM scenario. Combining the electroweak vacuum stability condition, the LHC Run-2 bounds, and the cosmological constraint from the observed DM relic density, we find that all constraints work together to narrow the allowed parameter regions and, in particular, exclude $m_{Z^{\prime }}\lesssim 3.5\mathrm{TeV}$. For the obtained allowed regions, we calculate the spin-independent cross section of the RHN DM with nucleons. We find that the resultant cross section is well below the current experimental upper bounds.

Theoretical investigations of the pentaquark states that were recently discovered provide important information on their nature and structure. It is necessary to study the spectroscopic parameters, like masses and residues of particles belong to the class of pentaquarks, and ones having similar structures. The mass and pole residue are quantities that emerge as the main input parameters in exploration of the electromagnetic strong and weak interactions of the pentaquarks with other hadrons in many frameworks. This work deals with a QCD sum rule analysis of the spin-$3/2$ and spin-$5/2$ bottom pentaquarks with both positive and negative parities aiming to evaluate their masses and residues. In calculations, the pentaquark states are modeled by molecular-type interpolating currents: for particles with $J=5/2$, a mixing current is used. We compare the results obtained in this work with the existing predictions of other theoretical studies. The predictions on the masses may shed light on experimental searches of the bottom pentaquarks.

In this paper we consider the production of proton-antiproton pairs in two-photon interactions in electron-positron and heavy-ion collisions. We try to understand the dependence of the total cross section on the photon-photon c.m. energy as well as corresponding angular distributions measured by the Belle Collaboration for the $\gamma \gamma \to p\overline{p}$ process. To understand the Belle data we include the proton-exchange, the $f_2(1270)$ and $f_2(1950)$ $s$-channel exchanges, as well as the hand-bag mechanism. The helicity amplitudes for the $\gamma \gamma \to f_2\to p\overline{p}$ process are written explicitly based on a Lagrangian approach. The parameters of vertex form factors are adjusted to the Belle data. Having described the angular distributions for the $\gamma \gamma \to p\overline{p}$ process we present first predictions for the ultraperipheral, ultrarelativistic, heavy-ion reaction ${}^{208}Pb{}^{208}Pb\to {}^{208}Pb{}^{208}Pbp\overline{p}$. Both, the total cross section and several differential distributions for experimental cuts corresponding to the ALICE, ATLAS, CMS, and LHCb experiments are presented. We find the total cross section $100\mu \mathrm{b}$ for the ALICE cuts, $160\mu \mathrm{b}$ for the ATLAS cuts, $500\mu \mathrm{b}$ for the CMS cuts, and $104\mu \mathrm{b}$ taking into account the LHCb cuts. This opens a possibility to study the $\gamma \gamma \to p\overline{p}$ process at the LHC.

The process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}2{\pi }^0\gamma$ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using $454.3{\mathrm{fb}}^{-1}$ of data collected around a center-of-mass energy of $\sqrt{s}=10.58\mathrm{GeV}$ by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as $(g_{\mu }^{{\pi }^{+}{\pi }^{-}2{\pi }^0}-2)/2=(17.9\pm {0.1}_{\mathrm{stat}}\pm {0.6}_{\mathrm{syst}})\times {10}^{-10}$ in the energy range $0.85\mathrm{GeV}<E_{\mathrm{CM}}<1.8\mathrm{GeV}$. In the same energy range, the impact on the running of the fine-structure constant at the $Z^0$-pole is determined as $\mathrm{\Delta }{\alpha }^{{\pi }^{+}{\pi }^{-}2{\pi }^0}(M_{\mathrm{Z}}^2)=(4.44\pm {0.02}_{\mathrm{stat}}\pm {0.14}_{\mathrm{syst}})\times {10}^{-4}$. Furthermore, intermediate resonances are studied and especially the cross section of the process $e^{+}{e}^{-}\to \omega {\pi }^0\to {\pi }^{+}{\pi }^{-}2{\pi }^0$ is measured.

The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of $190\mu {\mathrm{b}}^{-1}$ of minimum-bias events collected with proton-proton collisions at a center-of-mass energy $\sqrt{s}=7\mathrm{TeV}$ in the early low-luminosity data taking with the ATLAS detector at the LHC.

A search for the solar neutrino effective magnetic moment has been performed using data from 1291.5 days exposure during the second phase of the Borexino experiment. No significant deviations from the expected shape of the electron recoil spectrum from solar neutrinos have been found, and a new upper limit on the effective neutrino magnetic moment of ${\mu }_{\nu }^{\mathrm{eff}}<{2.8\times 10}^{-11}$ ${\mu }_B$ at 90% C.L. has been set using constraints on the sum of the solar neutrino fluxes implied by the radiochemical gallium experiments. Using the limit for the effective neutrino moment, new limits for the magnetic moments of the neutrino flavor states, and for the elements of the neutrino magnetic moments matrix for Dirac and Majorana neutrinos, are derived.

To study the effect of parity violation on the rate of complexity growth, by using “$\text{complexity}=\text{action}$” conjecture, we find the complexity growth rates in different solutions of the chiral theory of topologically massive gravity (TMG) and parity-preserving theory of new massive gravity (NMG). Using the results, one can see that decreasing the parameter $\mu$, which increases the effect of the Chern-Simons term and increases chirality, would increase the rate of growth of complexity. Also one can observe a stronger correlation between complexity growth and temperature rather than complexity growth and entropy. At the end we comment on the possible meaning of the deforming term of chiral Liouville action for the rate of complexity growth of warped conformal field theories in the tensor network renormalization picture.

We discuss various realizations of the Weyl group in the background field expansion of quantum gravity, in the presence of a cutoff, as required in applications of the functional renormalization group. To study the background dependence, special attention is given to split gauge transformations, which act on the background field and fluctuation keeping the total metric unchanged. The results generalize previous works on global and local scale transformations.

We extend the holographic analysis of the light-baryon spectrum by Cai et al. [Phys. Rev. D 90, 106001 (2014)] to the case involving the heavy flavors. With the construction of the Witten-Sakai-Sugimoto model in the D0-D4 background, we use the mechanism proposed by Liu and Zahed by including two light-flavor and one heavy-flavor brane, to describe the heavy-light baryons as heavy mesons bound to a flavor instanton. The background geometry of this model corresponds to an excited state in the dual field theory with a nonzero glue condensate $⟨\mathrm{Tr}\mathcal{F}\wedge \mathcal{F}⟩=8{\pi }^2{N}_c\tilde{\kappa }$ (or equivalently a nonzero $\theta$ angle), which is proportional to the number density of the D0-brane charge. In the strong-coupling limit, this model shows that the heavy meson is always bound in the form of the zero mode of the flavor instanton in the fundamental representation. We systematically study the quantization of the effective Lagrangian of heavy-light baryons by employing the soliton picture, and derive the mass spectrum of heavy-light baryons in the situation with single- and double-heavy baryons. We find that the difference in the mass spectrum becomes smaller if the density of the D0-brane charge increases, and the stability constraint of the heavy-light baryons is $1<b<3$. This indicates that a baryon cannot stably exist for a sufficiently large D0 charge density, which is in agreement with the conclusions in the previous study of this model.

We provide a full quantization of the vacuum Gowdy model with local rotational symmetry. We consider a redefinition of the constraints where the Hamiltonian Poisson-commutes with itself. We then apply the canonical quantization program of loop quantum gravity within an improved dynamics scheme. We identify the exact solutions of the constraints and the physical observables, and we construct the physical Hilbert space. It is remarkable that quantum spacetimes are free of singularities. New quantum observables naturally arising in the treatment partially codify the discretization of the geometry. The preliminary analysis of the asymptotic future/past of the evolution indicates that the existing Abelianization technique needs further refinement.

We study spontaneous supersymmetry breaking in spatially modulated stable or metastable vacua in supersymmetric field theories. Such spatial modulation can be realized in a higher derivative chiral model for which vacuum energies are positive, negative, or zero, depending on the model parameters. There appears a Nambu-Goldstone boson associated with the spontaneous breaking of the translational and $U(1)$ symmetries without the quadratic kinetic term and with a quartic derivative term in the modulated direction, and a gapless Higgs mode. We show that there appears a Goldstino associated with the supersymmetry breaking at a metastable vacuum, where energy is positive, while it becomes a fermionic ghost in the negative energy vacuum, and zero norm state and disappears from the physical sector in the zero energy vacuum.

The relative entropy between very high-energy localized excitations and the vacuum, where both states are reduced to a spatial region, gives place to a precise definition of a local temperature produced by vacuum entanglement across the boundary. This generalizes the Unruh temperature of the Rindler wedge to arbitrary regions. The local temperatures can be read off from the short distance leading have a universal geometric expression that follows by solving a particular eikonal type equation in Euclidean space. This equation generalizes to any dimension the holomorphic property that holds in two dimensions. For regions of arbitrary shapes the local temperatures at a point are direction dependent. We compute their explicit expression for the geometry of a wall or strip.

We present measurements of the fractal dimension of a turbulent asymptotically anti–de Sitter black brane reconstructed from simulated boundary fluid data at the perfect fluid order using the fluid-gravity duality. We argue that the boundary fluid energy spectrum scaling as $E(k)\sim k^{-2}$ is a more natural setting for the fluid-gravity duality than the Kraichnan-Kolmogorov scaling of $E(k)\sim k^{-5/3}$, but we obtain fractal dimensions $D$ for spatial sections of the horizon $H\cap \mathrm{\Sigma }$ in both cases: $D=2.584(1)$ and $D=2.645(4)$, respectively. These results are consistent with the upper bound of $D=3$, thereby resolving the tension with the recent claim in Adams et al. [Phys. Rev. Lett. 112, 151602 (2014)] that $D=3+1/3$. We offer a critical examination of the calculation which led to their result, and show that their proposed definition of the fractal dimension performs poorly as a fractal dimension estimator on one-dimensional curves with known fractal dimension. Finally, we describe how to define and in principle calculate the fractal dimension of spatial sections of the horizon $H\cap \mathrm{\Sigma }$ in a covariant manner, and we speculate on assigning a “bootstrapped” value of fractal dimension to the entire horizon $H$ when it is in a statistically quasisteady turbulent state.

The mass per unit length of a cylindrical system can be found from its external metric as can its angular momentum. Can the fluxes of energy, momentum, and angular momentum along the cylinder also be so found? We derive the metric of a beam of circularly polarized electromagnetic radiation from the Einstein-Maxwell equations. We show how the uniform plane wave solutions miss the angular momentum carried by the wave. We study the energy, momentum, angular momentum, and their fluxes along the cylinder both for this beam and in general. The three Killing vectors of any stationary cylindrical system give three Komar flux vectors which in turn give six conserved fluxes. We elucidate Komar’s mysterious factor 2 by evaluating Komar integrals for systems that have no trace to their stress tensors. The Tolman-Komar formula gives twice the energy for such systems which also have twice the gravity. For other cylindrical systems their formula gives correct results.

The field equations of $f(R)$ gravity are rewritten in the form of obvious wave equations with the stress-energy pseudotensor of the matter fields and the gravitational field as its source under the de Donder condition. The method of multipole analysis in terms of irreducible Cartesian tensors is applied to the linearized $f(R)$ gravity, and its multipole expansion is presented explicitly. In this expansion, the tensor part is symmetric and trace-free and is the same as that in General Relativity, and the scalar part predicts the appearance of monopole and dipole radiation in $f(R)$ gravity, as shown in literature. As a by-product, the multipole expansion for the massive Klein-Gordon field with an external source in terms of irreducible Cartesian tensors and its corresponding stationary results are provided.

We study ultrahigh-energy particle collisions and optical effects in the extraordinary class of mining braneworld Kerr-Newman (KN) naked singularity spacetimes, predicting extremely high efficiency of Keplerian accretion, and compare the results to those related to the other classes of the KN naked singularity and black hole spacetimes. We demonstrate that in the mining KN spacetimes the ultrahigh center-of-mass energy occurs for collisions of particles following the extremely-low-energy stable circular geodesics of the “mining regime,” colliding with large family of incoming particles, e.g., those infalling from the marginally stable counter-rotating circular geodesics. This is qualitatively different situation in comparison to the standard KN naked singularity or black hole spacetimes where the collisional ultrahigh center-of-mass energy can be obtained only in the near-extreme spacetimes. We also show that observers following the stable circular geodesics of the mining regime can register extremely blue-shifted radiation incoming from the Universe, and see strongly deformed sky due to highly relativistic motion along such stable orbits. The strongly blue-shifted radiation could be thus a significant source of energy for such orbiting observers.

In this work we shall investigate the cosmological dynamical system of $f(R)$ gravity, by constructing it in such a way so that it is rendered autonomous. We shall study the vacuum $f(R)$ gravity case, but also the case that matter and radiation perfect fluids are present along with the $f(R)$ gravity. The dynamical system is constructed in such a way that the time dependence of the system is contained in a single parameter which depends on the Hubble rate and its second derivative. The autonomous structure of the dynamical system is achieved when this parameter is constant; therefore we focus on these cases. For the vacuum $f(R)$ case, we investigate two cases with the first leading to a stable de Sitter attractor fixed point but also to an unstable de Sitter fixed point, and the second is related to a matter dominated era. The stable de Sitter attractor is also found for the $f(R)$ gravity in the presence of matter and radiation perfect fluids. In all the cases we perform a detailed numerical analysis of the dynamical system, and we also investigate in detail the stability of the resulting fixed points. Also, we present an exceptional feature of the $R^2$ gravity model, in the absence of perfect fluids. Finally, we investigate what is the approximate form of the $f(R)$ gravities near the stable and the unstable de Sitter fixed points.

We develop the foundations of an effective-one-body (EOB) model for eccentric binary coalescences that includes the conservative dynamics, radiation reaction, and gravitational waveform modes from the inspiral and the merger-ringdown signals. Our approach uses the strategy that is commonly employed in black-hole perturbation theory: we introduce an efficient, relativistic parameterization of the dynamics that is defined by the orbital geometry and consists of a set of phase variables and quantities that evolve only due to gravitational radiation reaction. Specializing to nonspinning binaries, we derive the EOB equations of motion for the new variables and make use of the fundamental frequencies of the motion to compute the binary’s radiative multipole moments that determine the gravitational waves. Our treatment has several advantages over the quasi-Keplerian approach that is often used in post-Newtonian (PN) calculations: a smaller set of variables, parameters that reflect the features of strong-field dynamics, and a greater transparency of the calculations when using the fundamental frequencies that leads to simplifications and an unambiguous orbit-averaging operation. While our description of the conservative dynamics is fully relativistic, we limit explicit derivations in the radiative sector to 1.5PN order for simplicity. This already enables us to establish methods for computing both instantaneous and hereditary contributions to the gravitational radiation in EOB coordinates that have straightforward extensions to higher PN order. The weak-field, small eccentricity limit of our results for the orbit-averaged fluxes agrees with known PN results when expressed in terms of gauge-invariant quantities. We further address considerations for the numerical implementation of the model and the completion of the waveforms to include the merger and ringdown signals, and provide illustrative results.