# The European Physical Journal C

## List of Papers (Total 3,037)

#### On the gravitational seesaw in higher-derivative gravity

Local gravitational theories with more than four derivatives are superrenormalizable. They also may be unitary in the Lee–Wick sense. Thus it is relevant to study the low-energy properties of these theories, especially to identify observables which might be useful for experimental detection of higher derivatives. Using an analogy with the neutrino physics, we explore the ...

#### Energy conditions of non-singular black hole spacetimes in conformal gravity

Conformal gravity can elegantly solve the problem of spacetime singularities present in Einstein’s gravity. For every physical spacetime, there is an infinite family of conformally equivalent singularity-free metrics. In the unbroken phase, every non-singular metric is equivalent and can be used to infer the physical properties of the spacetime. In the broken phase, a Higgs-like ...

#### Heat engines for dilatonic Born–Infeld black holes

In the context of dilaton coupled Einstein gravity with a negative cosmological constant and a Born–Infeld field, we study heat engines where a charged black hole is the working substance. Using the existence of a notion of thermodynamic mass and volume (which depend on the dilaton coupling), the mechanical work takes place via the pdV terms present in the first law of extended ...

#### Top quark electroweak couplings at future lepton colliders

We perform a comparative study of the reach of future $e^+e^-$ collider options for the scale of non-resonant new physics effects in the top quark sector, phrased in the language of higher-dimensional operators. Our focus is on the electroweak top quark pair production process $e^+e^- \rightarrow Z^*/\gamma \rightarrow t\bar{t}$, and we study benchmark scenarios at the ILC and ...

#### What is the scale of new physics behind the B-flavour anomalies?

Motivated by the recent hints of lepton flavour non-universality in B-meson semi-leptonic decays, we study the constraints of perturbative unitarity on the new physics interpretation of the anomalies in $b \rightarrow c \ell \bar{\nu }$ and $b \rightarrow s \ell \bar{\ell }$ transitions. Within an effective field theory approach we find that $2 \rightarrow 2$ fermion ...

#### f(R) constant-roll inflation

The previously introduced class of two-parametric phenomenological inflationary models in general relativity in which the slow-roll assumption is replaced by the more general, constant-roll condition is generalized to the case of f(R) gravity. A simple constant-roll condition is defined in the original Jordan frame, and exact expressions for a scalaron potential in the Einstein ...

#### Gravitational perfect fluid collapse in Gauss–Bonnet gravity

The Einstein Gauss–Bonnet theory of gravity is the low-energy limit of heterotic super-symmetric string theory. This paper deals with gravitational collapse of a perfect fluid in Einstein–Gauss–Bonnet gravity by considering the Lemaitre–Tolman–Bondi metric. For this purpose, the closed form of the exact solution of the equations of motion has been determined by using the ...

#### Cosmic structure sizes in generic dark energy models

The maximum allowable size of a spherical cosmic structure as a function of its mass is determined by the maximum turn around radius $R_\mathrm{TA,max}$, the distance from its center where the attraction on a radial test particle due to the spherical mass is balanced with the repulsion due to the ambient dark energy. In this work, we extend the existing results in several ...

#### Effective action for reggeized gluons, classical gluon field of relativistic color charge and color glass condensate approach

We discuss application of formalism of small-x effective action for reggeized gluons (Gribov, Sov. Phys. JETP 26:414, 1968; Lipatov, Nucl. Phys. B 452:369, 1995; Lipatov, Phys. Rep. 286:131, 1997; Lipatov, Subnucl. Ser. 49:131, 2013; Lipatov, Int. J. Mod. Phys. Conf. Ser. 39:1560082, 2015; Lipatov, Int. J. Mod. Phys. A 31(28/29):1645011, 2016; Lipatov, EPJ Web Conf. 125:01010, ...

#### Covariant generalized holographic dark energy and accelerating universe

We propose the generalized holographic dark energy model where the infrared cutoff is identified with the combination of the FRW universe parameters: the Hubble rate, particle and future horizons, cosmological constant, the universe lifetime (if finite) and their derivatives. It is demonstrated that with the corresponding choice of the cutoff one can map such holographic dark ...

#### Quintessence background for 5D Einstein–Gauss–Bonnet black holes

As we know that the Lovelock theory is an extension of the general relativity to the higher-dimensions, in this theory the first- and the second-order terms correspond to general relativity and the Einstein–Gauss–Bonnet gravity, respectively. We obtain a 5D black hole solution in Einstein–Gauss–Bonnet gravity surrounded by the quintessence matter, and we also analyze their ...

#### S-matrix formulation of thermodynamics with N-body scatterings

We apply a phase space expansion scheme to incorporate the N-body scattering processes in the S-matrix formulation of statistical mechanics. A generalized phase shift function suitable for studying the thermal contribution of $N \rightarrow N$ processes is motivated and examined in various models. Using the expansion scheme, we revisit how the hadron resonance gas model emerges ...

#### An alternative perspective to observe the critical phenomena of dilaton black holes

The critical phenomena of dilaton black holes are probed from a totally different perspective other than the P–v criticality and the q–U criticality discussed in former literature. We investigate not only the two point correlation function but also the entanglement entropy of dilaton black holes. For both the two point correlation function and the entanglement entropy we consider ...

#### Effective horizons, junction conditions and large-scale magnetism

The quantum mechanical generation of hypermagnetic and hyperlectric fields in four-dimensional conformally flat background geometries rests on the simultaneous continuity of the effective horizon and of the extrinsic curvature across the inflationary boundary. The junction conditions for the gauge fields are derived in general terms and corroborated by explicit examples with ...

#### The next 16 higher spin currents and three-point functions in the large $\mathcal{N}=4$ holography

By using the known operator product expansions (OPEs) between the lowest 16 higher spin currents of spins $(1, \frac{3}{2}, \frac{3}{2}, \frac{3}{2}, \frac{3}{2}, 2,2,2,2,2,2, \frac{5}{2}, \frac{5}{2}, \frac{5}{2}, \frac{5}{2}, 3)$ in an extension of the large $\mathcal{N}=4$ linear superconformal algebra, one determines the OPEs between the lowest 16 higher spin currents in an ...

#### Perturbative evolution: a different approach at small x

We propose an approach to DGLAP evolution at small x that circumvents the usual problem that a perturbation expansion is not valid there. The data for the charm structure function are important to motivate the method, and it describes them much more successfully than the conventional approach.

#### A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties

We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron–positron annihilation. This determination, performed at leading, next-to-leading, and next-to-next-to-leading order in perturbative QCD, is based on the NNPDF methodology, a ...

#### Einstein–Maxwell-axion theory: dyon solution with regular electric field

In the framework of the Einstein–Maxwell-axion theory we consider static spherically symmetric solutions which describe a magnetic monopole in the axionic environment. These solutions are interpreted as the solutions for an axionic dyon, the electric charge of which is composite, i.e. in addition to the standard central electric charge it includes an effective electric charge ...

#### Forward two-photon exchange in elastic lepton–proton scattering and hyperfine-splitting correction

We relate the forward two-photon exchange (TPE) amplitudes to integrals of the inclusive lepton–proton scattering cross sections. These relations yield an alternative way for the evaluation of the TPE correction to hyperfine-splitting (HFS) in the hydrogen-like atoms with an equivalent to the standard approach (Iddings, Drell and Sullivan) result implying the Burkhardt–Cottingham ...

In a perturbative QCD approach we study the direct CP violation in the pure annihilation decay process of $\bar{B}^0_{s}\rightarrow \pi ^+\pi ^-\pi ^+\pi ^-$ induced by the $\rho$ and $\omega$ double resonance effect. Generally, the CP violation is small in the pure annihilation type decay process. However, we find that the CP violation can be enhanced by double $\rho ... #### On the choice of beam polarization in \(e^+e^-\rightarrow ZZ/Z\gamma$ and anomalous triple gauge-boson couplings

The anomalous trilinear gauge couplings of Z and $\gamma$ are studied in $e^+e^-\rightarrow ZZ/Z\gamma$ with longitudinal beam polarizations using a complete set of polarization asymmetries for the Z boson. We quantify the goodness of the beam polarization in terms of the likelihood and find the best choice of $e^-$ and $e^+$ polarizations to be ($+0.16$, $-0.16$), ...

#### On new bulk singularity structures, RR couplings in the asymmetric picture and their all order $\alpha '$ corrections

We have analyzed in detail four and five point functions of the string theory amplitudes, including a closed string Ramond–Ramond (RR) in an asymmetric picture and either two or three transverse scalar fields in both IIA and IIB. The complete forms of these S-matrices are derived and these asymmetric S-matrices are also compared with their own symmetric results. This leads us to ...