A remark on the coupling of the ρ-trajectory to the π-π system

A finite energy sum rule for theπ-π scattering suggests that theρ-trajectory chooses nonsense at the point α_ρ=0, and that the spin of theg(1650) meson isJ ^p =1^?.     

A remark on the boson-fermion correspondence

We introduce the space of skew-symmetric functions depending on an infinite number of variables and give a simple interpretation of the boson-fermion correspondence.     

A remark on the Dirac equation

We give a simple deductive derivation of the Dirac equation for a free particle. Our construction provides a clear distinction between what are the physical contents and what are purely mathematical expedients in the formalism of quantum mechanics (QM).     

A remark on the cluster theorem

An improved version of the cluster theorem of relativistic quantum field theory with the correct exponential decay is derived by function theoretical methods.Heisenberg fellowLaboratoire propre du Centre National de la Recherche Scientifique     

A remark on the concavity of entropy

We investigate to what extent theorems about quantum mechanical or classical entropy can be generalized to functionals of the type ρ→Tr f(ρ), or ψ→∫f(ψ)dμ, respectively, wheref is an arbitrary concave function.     

A remark on the generalized Goldberg-Sachs theorem

Despite the elegant formulations of Kundt and Thompson[1], and Robinson and Schild[2], it is not obvious how general the generalized GoldbergSachs theorem[3] really is. A spacetime satisfying Einstein's equations with a null fluid source, for example, can elude the generalized theorem if, and only if, the null direction of the fluid is a fourfold repeated principal null direction of the Weyl tensor. An example of such a spacetime is presented.     

A remark on null infinity

It is shown that to each choice of conformal factor for the conformal metric on future null Infinity (₊) there is associated an equivalence class of slicings of ₊. Each slicing in turn gives rise to a family of null hypersurfaces in the physical space-time.Supported by NSF Grant No. GP-35773X1.     

A remark on SU4

Several of the interesting new relations in elementary particle physics discovered from the hypothesis of SU₆ symmetry of strong interactions, are shown to follow from the less restrictive assumption of SU₄ symmetry alone. Since isospin invariance is a much more closely obeyed symmetry than SU₃, these relations may be the best tests for the validity of combining internal symmetries with spin.     

A remark on tensor representations

The identity $$\sum\limits_{v = 0} {\left( {\begin{array}{*{20}c} {n + 1} \\ v \\ \end{array} } \right)\left[ {\left( {\begin{array}{*{20}c} {n - v} \\ v \\ \end{array} } \right) - \left( {\begin{array}{*{20}c} {n - v} \\ {v - 1} \\ \end{array} } \right)} \right] = ( - 1)^n } $$ is proved and, by means of it, the coefficients of the decomposition ofD ₁ ⁿ into irreducible representations are found. It holds: ifD ₁ ⁿ \(\mathop {\sum ^n }\limits_{m = 0} A_{nm} D_m \) , then $$A_{nm} = \mathop \sum \limits_{\lambda = 0} \left( {\begin{array}{*{20}c} n \\ \lambda \\ \end{array} } \right)\left[ {\left( {\begin{array}{*{20}c} \lambda \\ {n - m - \lambda } \\ \end{array} } \right) - \left( {\begin{array}{*{20}c} \lambda \\ {n - m - \lambda - 1} \\ \end{array} } \right)} \right].$$      

A remark on transition probability

Uhlmann's transition probability P(ψ, φ) of two normal states of a von Neumann algebra M, which is the supremum of |(Ψ, Φ)|² for all possible choices of representative vectors Ψ and Φ of ψ and φ, is shown to be the infimum of (∫d(μ_{ψ, e})^1/2)² for the induced measures μ_{ω, e}(B)=ω(e(B)) (B: Borel set in ℝ, ω=ψ, φ) for all possible projection-valued measures e belonging to M.     

A remark on quantum gravity

We discuss the structure of Dyson-Schwinger equations in quantum gravity and conclude in particular that all relevant skeletons are of first order in the loop number. There is an accompanying sub-Hopf algebra on gravity amplitudes equivalent to identities between n-graviton scattering amplitudes which generalize the Slavnov-Taylor identities. These identities map the infinite number of charges and finite numbers of skeletons in gravity to an infinite number of skeletons and a finite number of charges needing renormalization. Our analysis suggests that gravity, regarded as a probability conserving but perturbatively non-renormalizable theory, is renormalizable after all, thanks to the structure of its Dyson-Schwinger equations.     

A remark on the scattering of BPS monopoles

It is shown that the classical dynamics of several slowly moving monopoles corresponds to a geodesic motion in the manifold of exact, static multi-monopole configurations.     

A remark on quasi-triangular Lie algebras

Quasi-triangular quantum Lie algebras are algebras of quantum Lie derivatives. We show how to associate a quasi-triangular quantum Lie algebra to any quantum group defined by exchange relations. This provides a systematical way for constructing bi-covariant differential calculus on exchange quantum groups.     

A remark on neutron slowing down

Using the integral representation of Dirac-function the densityW _n(U) of the neutron lethargy probability distribution after then ^th collision with nuclei of a moderator has been found. The assumption has been made that the collisions are elastic and lethargy increments in individual collisions are independent. This procedure leads to expression ofW _n(U) by an improper integral which is in turn converted to a finite sum. Further the asymptotic behaviour ofW _n(U) for great number of collisionsn has been determined.Ronov pod Radhotm, Czechoslovakia.     

A remark on the polar decomposition ofm-sectorial operators

It is shown that the spectrum of the unitary partU of the polar decomposition of am-sectorial operatorA=UK is contained in the closure of {(x|Ax):xD(A)}.     

A remark on the third law of thermodynamics

It is shown that Falk's formulation of the third law of thermodynamics (when the energy has minimum value the entropy is also minimum) can be replaced by an equivalent assertion: the absolute minimum energy is unattainable with a finite number of processes.

---

,

( , ) : .

     

A remark on the hydrodynamics of the zero-range processes

The nonequilibrium stationary hydrodynamical properties of the symmetric nearest neighbor zero-range processes are studied: local equilibrium and Fourier's law are proven to hold, and the bulk diffusion coefficient and the equal time covariance of the limiting nonequilibrium stationary density fluctuations field are computed. The result fits with those already known and confirms some conjectures derived from a time-dependent macroscopic analysis. The very simple proof is based on a result already published but may be not so well known in this context.Partially supported by NATO Grant No. 040.82.Partially supported by FAPESP: Fundacão de Amparo à Pesquisa do Estado de São Paulo, Grant No. 82/1719-9.