Itamar Assumpção me lembra uma São Paulo que só existe dentro da minha cabeça

www.youtube.com/watch?v=q2Xw...

Does scalar gravity obey the equivalence principle?

2005: You can't trust anything that's on Wikipedia
2025: You can't trust anything besides Wikipedia

A deep remark: "Once a tree approximation (corresponding to a consistent classical field theory) is known, the full quantum theory is in principle determined by unitarity" (Green Schwarz & Witten, Superstring Theory Vol 1, p. 353).

Quantum mechanics = classical mechanics + unitarity?

Using Pochhammer countours to perform an analytical continuation of the Veneziano amplitude, we find that the poles are incorporated in a denominator (1 - exp{-2πiα's}). This seems to diverge for all α's integer, while the amplitude should have poles only in the physical spectrum. Why is this?

When using unitarity to compute 1-loop amplitudes, how do you make sure that unphysical polarizations do not contribute in the intermediate states?

I should - really - learn how to be confortable with the heat kernel.

Given some set of 2nd order constraints {Φ_a} of some phase space (q^i, p_i), how to get the Dirac bracket as the pullback to the constrained surface?

Você pode dar um emprego a um homem, mas não pode arrancar de dentro dele a vontade de ser desempregado

Today I will start reading the little book "Scattering Amplitudes" by H. Elvang and Y. Huang

This is a long thread for a chapter-by-chapter review and a reading guide for volume 1 of Polchinski’s book on string theory. Familiarity with the basics of QFT and GR is required (you will need these pre-requisites to read the book anyway)
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#physics #scicomm

Ana lives on the n-sphere, very close the origin. There is a +q charge at the origin, and a -q charge at infinity. Bruno lives on the usual R^n, and there is a +q charge at the origin.

Do Ana and Bruno see the same electric field?

Agora eu tenho um número 🚀🚀

Não consigo abrir uma conta de banco porque não tenho número de celular

Não consigo um número de celular porque não tenho uma conta de banco

Viajando de avião, dá pra notar que a elevação da base das nuvens de uma mesma região é sempre próxima, e elas sempre estão mais ou menos no mesmo nível. A distância entre a base e o topo das nuvens varia um pouco mais

Não gosto de me mudar

Também não gosto de viagens longas

How to explain why CPT is always preserved in simple terms?

The Poincaré group has a nontrivial subgroup that transforms into itself (the translations), so it is not simple. The conformal group, on the other hand, is simple. Are there any interesting implications of this fact?