We investigate the sensitivity of the solar model to changes in the nuclear reaction screening factors. We show that the sound speed profile as determined by helioseismology certainly rules out changes in the screening factors exceeding more than 10%. A slightly improved solar model could be obtained by enhancing screening by about 5% over the Salpeter value. We also discuss how envelope proper...

A system of U(N)-matrix difference equations is solved by means of a nested version of a generalized Bethe Ansatz. The highest weight property of the solutions is proved and some examples of solutions are calculated explicitly.

Non-linear integral equations derived from Bethe Ansatz are used to evaluate finite size corrections to the highest (i.e. anti-ferromagnetic) and immediately lower anomalous dimensions of scalar operators in N = 4 SYM. In specific, multi-loop corrections are computed in the SU (2) operator subspace, whereas in the general SO(6) case only one loop calculations have been finalised. In these cases...

Bethe-Salpeter equation in the non-commutative space for a scalarscalar bound state is considered. It is shown that in the non-relativistic limit, the effect of spatial non-commutativity appears as if there exist a magnetic dipole moment coupled to each particle. e-mail: [email protected] e-mail: [email protected] Non-commutativity of space-time has been recently a subject of intense ...

In theoretical hadron physics mesons are a center of attention. Constructed in a simpler way than baryons in the quark model, they still present a considerable challenge if one aims at an understanding of all their aspects in terms of quarks and gluons in the context of Quantum Chromodynamics, the quantum field theory of the strong interaction. Complementary to (constituent-) quark models, redu...

We study the electron-positron system in a strong magnetic field using the differential BetheSalpeter equation in the ladder approximation. We derive the fully relativistic two-dimensional form that the four-dimensional Bethe-Salpeter equation takes in the limit of asymptotically strong constant and homogeneous magnetic field. An ultimate value for the magnetic field is determined, which provid...

We reformulate the nested coordinate Bethe ansatz in terms of coproducts of Yangian symmetry generators. This allows us to derive the nested Bethe equations for the bound state string S-matrices. We find that they coincide with the Bethe equations obtained from a fusion procedure. The bound state number dependence in the Bethe equations appears through the parameters x± and the dressing phase o...

The spin chains originating from large-N conformal gauge theories are of a special kind: The Hamiltonian is not invariant under the symmetry algebra, it is rather a part of it. This leads to interesting properties within the asymptotic Bethe ansatz. Here we study an S-matrix with u(1|1) symmetry which arises in a long-range spin chain with fundamental spins of su(2|1).

We use the LSZ reduction theorem and interpolating fields, alongwith the heavy quark effective theory, to investigate the structure of the BetheSalpeter amplitude for heavy hadrons. We show how a simple form of this amplitude, used extensively in heavy hadron decay calculations, follows naturally upto O(1/M) from these field theoretic considerations. Accepted for publication in Physics Letters B