(First of all apologies for the long wall of text)(adsbygoogle = window.adsbygoogle || []).push({});

I am to study BRST transformations, for which I'm currently trying to understand constrained Hamiltonian dynamics to treat systems with singular Lagrangians. The crude recipe followed is Lagrangian -> Hamiltonian -> Dirac brackets and their quantization. I have been told that these techniques are used in QFT, string theory/high energy , etc.

My question is are these formalisms indeed good and useful to learn? I'm confused because there are other formalisms and recipes (for example directly working with the Lagrangian). From a modern perspective, are these relevant? And does there exist any other formalism that I should not ignore? I will be starting my graduation soon; is it late to be studying constrained H formalism/BRST?

(I want to know how beneficial it is to study constrained Hamiltonian approach, because I'm not sure whether it's obsolete, having been replaced by better approaches (like path integrals?) which I should rather pay attention to. I'm not even sure what is the extent of applicability of constrained Hamiltonian dynamics..)

Thanks

EDIT:Directly working with Lagrangian as in one doesn't bother with the Hamiltonian in that approach, direct quantization from the Lagrangian stage. I have also heard that there are other approaches like Feynman path integrals, etc. But I don't know about their relative merits, and that's what I want to be clear about.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Importance of constrained Hamilton dynamics and BRST transformations

**Physics Forums | Science Articles, Homework Help, Discussion**