Modern Physics Letters A

After the Higgs boson discovery in 2012, the investigation of its properties and compatibility with the Standard Model predictions is central to the physics program of the LHC experiments. Likewise, the study of the top quark is still relevant at the LHC, more than two decades after its discovery at the Tevatron. Top quarks and Higgs bosons are produced at the LHC on a large scale and share a deep connection based on the large mass of the top quark. Both particles provide an excellent laboratory in which to search for new physics: the measurement of their properties tests the foundations of the Standard Model; and they feature prominently in a variety of exotic signals. The coupling of the Higgs boson to the top quark, a fundamental Standard Model parameter, can only be measured directly in processes where the two particles are produced together. The production of a Higgs boson together with one or two top quarks is also sensitive to several exciting new physics effects. A brief overview of the current experimental status of top quark and Higgs boson physics is presented using results from the CMS Collaboration.

We discuss the effect of the dynamics of D-branes on moduli stabilization in type IIB string theory compactifications, with reference to a concrete toy model of $T^6/Z_3$ orientifold compactification with fractional D3-branes and anti-D3-branes at orbifold fixed points. The resulting attractive forces between anti-D3-branes and D3-branes, together with the repulsive forces between anti-D3-branes and O3-planes, can affect the stability of the compact space. There are no complex structure moduli in $T^6/Z_3$ orientifold, which should thus capture some generic features of more general settings where all complex structure moduli are stabilized by three-form fluxes. The simultaneous presence of branes and anti-branes brings along the breaking of supersymmetry. Non-BPS combinations of this type are typical of “brane supersymmetry breaking” and are a necessary ingredient in the KKLT scenario for stabilizing the remaining Kähler moduli. The conclusion of our analysis is that, while mutual D-brane interactions sometimes help Kähler moduli stabilization, this is not always the case.

The diquark–diquark–antiquark model describes pentaquark states both in terms of quarks and hadrons. The latest LHCb data for pentaquarks with open charm emphasize the importance of hadron components in the structure of pentaquarks. We discuss pentaquark states with hidden charm $P(\bar{c}cuud)$ and those with open charm $P(ūussc)$ which were discovered recently in LHCb data ($J/\mathrm{\Psi }p$ and ${\mathrm{\Xi }}_c^{+}{K}^{-}$ spectra correspondingly). Considering the observed states as members of the lowest ($s$-wave) multiplet, we discuss the mass splitting of states and the dumping of their widths.

The Regge spectrum of soft-wall holographic model is generalized to the case of arbitrary twist. Combining this result with the light-front holographic QCD, one arrives at a broad hydrogen-like degeneracy of the same sort as the degeneracy observed experimentally in the spectrum of light mesons.

In this paper, a study of the accelerated expansion problem of the large scale universe is presented. To derive Friedmann like equations, describing the background dynamics of the recent universe, we take into account, that it is possible to interpret the spacetime dynamics as an emergent phenomenon. It is a consequence of the deep study of connection between gravitation and thermodynamics. The models considered are based on phenomenological modifications of the horizon temperature. In general, there are various reasons to modify the horizon temperature, one of which is related to the feedback from the spacetime on the horizon, generating additional heat. In order to constrain the parameters of the models, we use Om analysis and the constraints on this parameter at z = 0.0, z = 0.57 and z = 2.34.

We suggest a method to compute the correlation functions in conformal quantum mechanics (CFT₁) for the fields that transform under a nonlocal representation of $𝔰𝔩(2)$ basing on the invariance properties. Explicit calculations of two- and three-point correlation functions are presented.

In this paper, we presented a noncommutative (NC) generalization of nonlinear Schrödinger equation (NLSE) in 2 + 1 dimensions. A matrix Darboux transformation (MDT) is used to generate multiple soliton solutions for NC-NLSE and commutative NLSE in 2 + 1 dimensions. We expressed multiple soliton solutions in terms of quasideterminants and as ratios of ordinary determinants for NC and commutative NLSE in 2 + 1 dimensions, respectively. The quasideterminant formula for K-times repeated MDT enables us to compute single, double and triple soliton solutions for NC and commutative (2 + 1)-dimensional NLSE. Some interesting localized solutions are obtained for the NC and commutative NLSE in 2 + 1 dimensions.