# The European Physical Journal C

## List of Papers (Total 3,037)

#### Ambitwistor superstring in the Green–Schwarz formulation

In this paper we construct the ambitwistor superstring in the Green–Schwarz formulation. The model is obtained from the related pure spinor version. We show that the spectrum contains only ten-dimensional supergravity and that kappa symmetry in a curved background implies some of the standard constraints.

#### Observational properties of rigidly rotating dust configurations

We study the observational properties of a class of exact solutions of Einstein’s field equations describing stationary, axially symmetric, rigidly rotating dust (i.e. non-interacting particles). We ask the question whether such solutions can describe astrophysical rotating dark matter clouds near the center of galaxies and we probe the possibility that they may constitute an ...

#### A chiral covariant approach to $\varvec{\rho \rho }$ scattering

We analyze vector meson–vector meson scattering in a unitarized chiral theory based on a chiral covariant framework restricted to $\rho \rho$ intermediate states. We show that a pole assigned to the scalar meson $f_0(1370)$ can be dynamically generated from the $\rho \rho$ interaction, while this is not the case for the tensor meson $f_2(1270)$ as found in earlier work. ...

#### Anisotropic SD2 brane: accelerating cosmology and Kasner-like space-time from compactification

Starting from an anisotropic (in all directions including the time direction of the brane) non-SUSY D2 brane solution of type IIA string theory we construct an anisotropic space-like D2 brane (or SD2 brane, for short) solution by the standard trick of a double Wick rotation. This solution is characterized by five independent parameters. We show that compactification on ...

#### Warm inflation with an oscillatory inflaton in the non-minimal kinetic coupling model

In the cold inflation scenario, the slow roll inflation and reheating via coherent rapid oscillation, are usually considered as two distinct eras. When the slow roll ends, a rapid oscillation phase begins and the inflaton decays to relativistic particles reheating the Universe. In another model dubbed warm inflation, the rapid oscillation phase is suppressed, and we are left with ...

#### The K-meson form factor and charge radius: linking low-energy data to future Jefferson Laboratory measurements

Starting from a successful model of the $\pi$-meson electromagnetic form factor, we calculate a similar form factor, $F_{K}(Q^{2})$, of the charged K meson for a wide range of the momentum transfer squared, $Q^{2}$. The only remaining free parameter is to be determined from the measurements of the K-meson charge radius, $r_{K}$. We fit this single parameter to the ...

#### Integrability from point symmetries in a family of cosmological Horndeski Lagrangians

For a family of Horndeski theories, formulated in terms of a generalized Galileon model, we study the integrability of the field equations in a Friedmann–Lemaître–Robertson–Walker space-time. We are interested in point transformations which leave invariant the field equations. Noether’s theorem is applied to determine the conservation laws for a family of models that belong to the ...

#### Dark matter phenomenology of SM and enlarged Higgs sectors extended with vector-like leptons

We will investigate the scenario in which the Standard Model (SM) Higgs sector and its two-doublet extension (called the Two Higgs Doublet Model or 2HDM) are the “portal” for the interactions between the Standard Model and a fermionic Dark Matter (DM) candidate. The latter is the lightest stable neutral particle of a family of vector-like leptons (VLLs). We will provide an ...

#### Heavy-quark form factors in the large $\beta _0$ limit

Heavy-quark form factors are calculated at $\beta _0 \alpha _s \sim 1$ to all orders in $\alpha _s$ at the first order in $1/\beta _0$. Using the inversion relation generalized to vertex functions, we reduce the massive on-shell Feynman integral to the HQET one. This HQET vertex integral can be expressed via a ${}_2F_1$ function; the nth term of its $\varepsilon$ ...

#### Exotic Higgs decay $h\rightarrow \phi \phi \rightarrow 4b$ at the LHeC

We study the exotic decay of the 125 GeV Higgs boson (h) into a pair of light spin-0 particles ($\phi$) which subsequently decay and result in a 4b final state. This channel is well motivated in models with an extended Higgs sector. Instead of searching at the Large Hadron Collider (LHC) and the high luminosity LHC (HL-LHC) which are beset by large standard model (SM) ...

#### Tachyon logamediate inflation on the brane

According to a Barrow solution for the scale factor of the universe, the main properties of the tachyon inflation model in the framework of the RSII braneworld are studied. Within this framework the basic slow-roll parameters are calculated analytically. We compare this inflationary scenario to the latest observational data. The predicted spectral index and the tensor-to-scalar ...

#### Excited scalar and pseudoscalar mesons in the extended linear sigma model

We present an in-depth study of masses and decays of excited scalar and pseudoscalar ${\bar{q}}q$ states in the Extended Linear Sigma Model (eLSM). The model also contains ground-state scalar, pseudoscalar, vector and axial-vector mesons. The main objective is to study the consequences of the hypothesis that the $f_0(1790)$ resonance, observed a decade ago by the BES ...

#### Rainbows without unicorns: metric structures in theories with modified dispersion relations

Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some ...

#### Chiral dynamics, S-wave contributions and angular analysis in $D\rightarrow \pi \pi \ell \bar{\nu }$

We present a theoretical analysis of the $D^-\rightarrow \pi ^+\pi ^- \ell \bar{\nu }$ and $\bar{D}^0\rightarrow \pi ^+\pi ^0 \ell \bar{\nu }$ decays. We construct a general angular distribution which can include arbitrary partial waves of $\pi \pi$. Retaining the S-wave and P-wave contributions we study the branching ratios, forward–backward asymmetries and a few other ...

#### Models of collapsing and expanding anisotropic gravitating source in f(R, T) theory of gravity

In this paper, we have formulated the exact solutions of the non-static anisotropic gravitating source in f(R, T) gravity which may lead to expansion and collapse. By assuming there to be no thermal conduction in gravitating source, we have determined parametric solutions in f(R, T) gravity with a non-static spherical geometry filled using an anisotropic fluid. We have examined the ...

#### Higher-dimensional inhomogeneous perfect fluid collapse in f(R) gravity

This paper is about the $n+2$-dimensional gravitational contraction of an inhomogeneous fluid without heat flux in the framework of a f(R) metric theory of gravity. Matching conditions for two regions of a star are derived by using the Darmois junction conditions. For the analytic solution of the equations of motion in modified f(R) theory of gravity, we have taken the scalar ...

#### Higher-twist effects in light-cone sum rule for the $B\rightarrow \pi$ form factor

We calculate the higher-twist corrections to the QCD light-cone sum rule for the $B \rightarrow \pi$ transition form factor. The light-cone expansion of the massive quark propagator in the external gluonic field is extended to include new terms containing the derivatives of the gluon-field strength. The resulting analytical expressions for the twist-5 and twist-6 contributions ...

#### Graviton propagation within the context of the D-material universe

Motivated by the recent breakthrough of the detection of Gravitational Waves (GW) from coalescent black holes by the aLIGO interferometers, we study the propagation of GW in the D-material universe, which we have recently shown to be compatible with large-scale structure and inflationary phenomenology. The medium of D-particles induces an effective mass for the graviton, as a ...

#### Anisotropic Weyl invariance

We consider a non-relativistic free scalar field theory with a type of anisotropic scale invariance in which the number of coordinates “scaling like time” is generically greater than one. We propose the Cartesian product of two curved spaces, the metric of each space being parameterized by the other space, as a notion of curved background to which the theory can be extended. We ...

#### Electroweak monopoles and the electroweak phase transition

We consider an isolated electroweak monopole solution within the Standard Model with a nonlinear Born–Infeld extension of the hypercharge gauge field. Monopole (and dyon) solutions in such an extension are regular and their masses are predicted to be proportional to the Born–Infeld mass parameter. We argue that cosmological production of electroweak monopoles may delay the ...

#### Physical attributes of anisotropic compact stars in f(R, G) gravity

Modified gravity is one of the potential candidates to explain the accelerated expansion of the universe. Current study highlights the materialization of anisotropic compact stars in the context of f(R, G) theory of gravity. In particular, to gain insight in the physical behavior of three stars namely, Her X1, SAX J 1808-3658 and 4U 1820-30, energy density, and radial and ...