New series representations for the two-loop massive sunset diagram

We derive new convergent series representations for the two-loop sunset diagram with three different propagator masses $$m_1,\, m_2$$m1,m2 and $$m_3$$m3 and external momentum p by techniques of analytic continuation on a well-known triple series that corresponds to the Lauricella $$F_C^{(3)}$$FC(3) function. The convergence regions of the new series contain regions of interest to physical problems. These include some ranges of masses and squared external momentum values which make them useful from Chiral Perturbation Theory to some regions of the parameter space of the Minimal Supersymmetric Standard Model. The analytic continuation results presented for the Lauricella series could be used in other settings as well.

Feynman Rules, Ward Identities and Loop Corrections in Very Special Relativity Standard Model

In this paper, we want to study one loop corrections in Very Special Relativity Standard Model(VSRSM). In order to satisfy the Ward identities and the S i m ( 2 ) symmetry of the model, we have to specify the Feynman rules, including the infrared regulator. To do this, we adapt the Mandelstam–Leibbrandt (ML) prescription to incorporate external momentum-dependent null vectors. As an example, we use the new S i m ( 2 ) invariant dimensional regularization to compute one loop corrections to the effective action in the subsector of the VSRSM that describe the interaction of photons with charged leptons. New stringent bounds for the masses of ν e and ν μ are obtained.

One-loop nonlinear correction for QED

In this work, we study the generation of a nonlinear correction for QED, namely, the Euler–Heisenberg effective action. In order to achieve this, we consider two methods. The first method employed consists in make use of Feynman parametrization to solve the integrals properly, while in the second method a derivative expansion in the external momentum was considered.

A Simple Technique to Infer the Missing Gravity Wave Drag in the Middle Atmosphere Using a General Circulation Model: Potential Vorticity Budget

A simple technique to infer the missing momentum forcing in a general circulation model is developed and evaluated. The response of the large-scale dynamic equations to an external momentum forcing presents a nonlocal response in the zonal and meridional wind. On the other hand, the response to the external momentum forcing in the potential vorticity (PV) is a local growing geostrophic mode, so that there is a direct relationship between the external momentum forcing and the response in PV. In this work, this fact is exploited to diagnose the missing momentum forcing in the extratropics using a general circulation model. The capability of the simple technique to estimate a concentrated gravity wave forcing is evaluated. A dynamical model is evolved with prescribed sources and sinks of PV and then the technique is used to estimate these known momentum sources and sinks. PV is found to give a much better diagnostic of gravity wave drag compared to the more traditional zonal wind differences. The technique is also used in a realistic environment, in which the sources and sinks of PV in Met Office analyses are determined. The estimation of this missing forcing with this simple technique is compared with the estimation given by a more complex data assimilation technique developed by Pulido and Thuburn and, in general, a good agreement is found. The simple gravity wave drag estimation technique can be used in an online data assimilation cycle, using the increments of the analysis, and also offline, using a general circulation model and observations.