The European Physical Journal C

http://link.springer.com/journal/10052

List of Papers (Total 2,952)

Casimir force in the Gödel space-time and its possible induced cosmological inhomogeneity

The Casimir force between two parallel plates in the Gödel universe is computed for a scalar field at finite temperature. It is observed that when the plates’ separation is comparable with the scale given by the rotation of the space-time, the force becomes repulsive and then approaches zero. Since it has been shown previously that the universe may experience a Gödel phase for a ...

Supersymmetric RG flows and Janus from type II orbifold compactification

We study holographic RG flow solutions within four-dimensional \(N=4\) gauged supergravity obtained from type IIA and IIB string theories compactified on \(T^6/\mathbb {Z}_2\times \mathbb {Z}_2\) orbifold with gauge, geometric and non-geometric fluxes. In type IIB non-geometric compactifications, the resulting gauged supergravity has \(ISO(3)\times ISO(3)\) gauge group and admits ...

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 ...

Post-Keplerian perturbations of the orbital time shift in binary pulsars: an analytical formulation with applications to the galactic center

We develop a general approach to analytically calculate the perturbations \(\Delta \delta \tau _\text {p}\) of the orbital component of the change \(\delta \tau _\text {p}\) of the times of arrival of the pulses emitted by a binary pulsar p induced by the post-Keplerian accelerations due to the mass quadrupole \(Q_2\), and the post-Newtonian gravitoelectric (GE) and Lense–Thirring ...

Understanding NaI(Tl) crystal background for dark matter searches

We have developed ultra-low-background NaI(Tl) crystals to reproduce the DAMA results with the ultimate goal of achieving purity levels that are comparable to or better than those of the DAMA/LIBRA crystals. Even though the achieved background level does not approach that of DAMA/LIBRA, it is crucial to have a quantitative understanding of the backgrounds. We have studied ...

Analytic solution of the Starobinsky model for inflation

We prove that the field equations of the Starobinsky model for inflation in a Friedmann–Lemaître–Robertson–Walker metric constitute an integrable system. The analytical solution in terms of a Painlevé series for the Starobinsky model is presented for the case of zero and nonzero spatial curvature. In both cases the leading-order term describes the radiation era provided by the ...

Compact bifluid hybrid stars: hadronic matter mixed with self-interacting fermionic asymmetric dark matter

The masses and radii of non-rotating and rotating configurations of pure hadronic stars mixed with self-interacting fermionic asymmetric dark matter are calculated within the two-fluid formalism of stellar structure equations in general relativity. The Equation of State (EoS) of nuclear matter is obtained from the density dependent M3Y effective nucleon–nucleon interaction. We ...

Remarks on a gauge theory for continuous spin particles

We discuss in a systematic way the gauge theory for a continuous spin particle proposed by Schuster and Toro. We show that it is naturally formulated in a cotangent bundle over Minkowski spacetime where the gauge field depends on the spacetime coordinate \({x^\mu }\) and on a covector \(\eta _\mu \). We discuss how fields can be expanded in \(\eta _\mu \) in different ways and how ...

What do we know about cosmography

In the present paper, we investigate the cosmographic problem using the bias–variance trade-off. We find that both the z-redshift and the \(y=z/(1+z)\)-redshift can present a small bias estimation. It means that the cosmography can describe the supernova data more accurately. Minimizing risk, it suggests that cosmography up to the second order is the best approximation. Forecasting ...

Possible signatures for tetraquarks from the decays of \(a_0(980)\) , \(a_0(1450)\)

Based on the recent proposal for the tetraquarks with the mixing scheme, we investigate fall-apart decays of \(a_0(980), a_0(1450)\) into two lowest-lying mesons. This mixing scheme suggests that \(a_0(980)\) and \(a_0(1450)\) are the tetraquarks with the mixtures of two spin configurations of diquark and antidiquark. Due to the relative sign differences in the mixtures, the ...

Top–antitop production from \(W^+_L W^-_L\) and \(Z_L Z_L\) scattering under a strongly interacting symmetry-breaking sector

By considering a non-linear electroweak chiral Lagrangian, including the Higgs, coupled to heavy quarks, and the equivalence theorem, we compute the one-loop scattering amplitudes \(W^+W^-\rightarrow t\bar{t}\), \(ZZ\rightarrow t\bar{t}\) and \(hh\rightarrow t\bar{t}\) (in the regime \(M_t^2/v^2\ll \sqrt{s}M_t/v^2\ll s/v^2\) and to NLO in the effective theory). We calculate the ...