arXiv subjects

H. Forkel

Publications and source records attributed to H. Forkel.

5 recordsLinked to original sources

arXiv2009

Dynamical holographic QCD with area-law confinement and linear Regge trajectories

We construct a new solution of five-dimensional gravity coupled to a dilaton which encodes essential features of holographic QCD backgrounds dynamically. In particular, it implements linear confinement, i.e. the area law behavior of the Wilson loop, by means of a dynamically deformed anti-de Sitter metric. The predicted square masses of the light-flavored natural-parity mesons and their excitations lie on linear trajectories of approximately universal slope with respect to both radial and spin quantum numbers and are in satisfactory agreement with experimental data.

hep-ph↗

arXiv2008

Solution of the 5D Einstein equations in a dilaton background model

We obtain an explicit solution of the 5d Einstein equations in a dilaton background model. We demonstrate that for each metric ansatz that only depends on the extra coordinate, it is possible to uniquely determine the dilaton field and its potential consistently with the 5d Einstein equation. In this holographic dual model of QCD, conformal symmetry of the Anti-de-Sitter metric near the 4d boundary is broken by a term that leads to an area law for the Wilson loop. We verify that confinement of the string modes dual to mesons follows from the metric background and the corresponding dilaton solution of the gravity-dilaton coupled equations. In addition, we show that the meson Regge trajectories constrain the metric and corresponding dilaton background within the area law requirement. We can also incorporate asymptotic freedom in the gravity background within the model.

hep-ph↗

arXiv2001

Instantons and Glueballs

We investigate the impact of instantons on scalar glueball properties in a largely model-independent analytical approach based on the instanton-improved operator product expansion (IOPE) of the $0^{++}$ glueball correlator. The instanton contributions turn out to be dominant, to substantially improve the consistency of the correponding QCD sum rules, and to increase the glueball residue about fivefold.

hep-ph↗

arXiv1999

Direct Instantons and Nucleon Magnetic Moments

We calculate the leading direct-instanton contributions to the operator product expansion of the nucleon correlator in a magnetic background field and set up improved QCD sum rules for the nucleon magnetic moments. Remarkably, the instanton contributions are found to affect only those sum rules which had previously been considered unstable. The new sum rules show good stability and reproduce the experimental values of the nucleon magnetic moments with values of $χ$, the quark condensate magnetic susceptibility, consistent with other estimates.

hep-ph↗

arXiv1998

K^* Mesons and Nucleon Strangeness

We study contributions to the nucleon strange quark vector current form factors from intermediate states containing K^* mesons. We show how these contributions may be comparable in magnitude to those made by K mesons, using methods complementary to those employed in quark model studies. We also analyze the degree of theoretical uncertainty associated with K^* contributions.

hep-ph↗