On rotations in front-form dynamics

Abstract

Quantum field theories in front-form dynamics are not manifestly rotationally invariant. We study a model bound-state equation in 3+1 dimensional front-form dynamics, which was shown earlier to reproduce the Bohr and hyperfine structure of positronium. We test this model with regard to its rotational symmetry and find that rotational invariance is preserved to a high degree. Also, we find and quantify the expected dependence on the cut-off.

Two-fermion relativistic bound states in light-front dynamics

“…Equation (10) from [38] gives for k max = 10 the value B DLC = 0.0308, in qualitative agreement -thought still sizeably different -with B QED . We should notice that a recent work [39] analyzes the results of [38] in terms of flow equations and obtains a closer value B DLC = 0.02341. We conclude from that, that the ladder LFD predictions for such a genuine system are unable to reproduce even the sign of first order relativistic corrections.…”

“…Our choice (35) is justified by the clear separation of n-independent and dependent terms it induces in the wave function (38). The normalization condition reads:…”

“…This approximation was used in [58,59] to calculate the NN S-wave function and deuteron electromagnetic form factors [61]. We will also present in what follows how these first order relativistic corrections can be obtained in the different mass equations (38), (61) we consider.…”

True muonium $({{\mu }^{+}}{{\mu }^{-}})$ on the light front

“…In this initial model of true muonium, we extend the Fock space considered in Refs. [14,[21][22][23] to include a second flavor of fermions: |µμ , |µμγ , |eē , |eēγ , and |γ . Through a proper choice of effective interactions [24], one can truncate the Fock space at these states and neglect other Fock states such as |γγ or |µμeē in a selfconsistent way.…”

On Deriving the Effective Interaction from the QCD Lagrangian

“…All of these methods are under active research. Applications particularly by Trittmann et al [13,14,15], Brisudova et al [16,17], Jones et al [18,19], and Gubankova et al [20] are presented elsewhere in these proceedings. Common to most of them is that one truncates the Fock space before approximation methods are applied.…”