Recent content by Urs Schreiber

Michael Duetsch's textbook on Mathematical Quantum Field Theory is finally out: nLab entry, publisher page . It refers to PF Insights, notably for the proof of renormalization via counterterms (theorem 3.4.9 in the book, referring to PF Insights, Chapter 16)

This is an FAQ: see What are the equations of string theory?

Thanks. Maybe it's an odd request, though it seems like something that must have occurred to others before. I am collecting references with quotes of roughly the kind I was asking for here.

I am looking for articles or books that would clearly and succinctly state the open problem of and issues with computing hadron masses and spins in QCD from first principles, preferably in relation to the open problem of confinement and the general open problem of non-perturbative QCD. Any...

Ultra-high cosmic rays hitting our atmosphere hardly provide a substitute for particle accelerator-like experiments, but they do show that ultra-high energy processes are common in the present epoch of the universe, and not confined to the "early moments of the big bang". There are some...

When you say that energies around 500,000 TeV "haven't existed" since around the big bang, you are thinking of average energies, hence of temperature scale. But for single particles such energies are not out of the question. The 500,000 TeV that you name is 0.5 EeV, and particles of energy a...

Today the reply from Kallosh and Linde: http://arxiv.org/abs/1809.09018 Am unsure about their logic. It sounds like saying it's not their problem if the embeddings into 10d of their model doesn't work. Instead they feel free to further modify the 4d model. Thomas von Riet comments (here): "it...

Further careful checks of the KKLT construction today, and further doubts that it can work: arxiv.org/1809.06861.

Today Moritz-Retolaza-Westphal arxiv.org/1809.06618 still aren't convinced of Kallosh-Linde's arguments for saving KKLT arxiv.org/1808.09428. Independent of how this debates turns out, the key point of Moritz-Retolaza-Westphal is simple: You got to stick to precise arguments. (possibly more...

Danielsson today in arxiv:1809.04512 linking the known instability of de Sitter in field theory (e.g. Rajaraman 16) to the issues with alleged dS string theory vacua. (He must have been following my comments here... ;-) Maybe there'll be more discussion here.

That's about right. In a sigma-model ("geometric") string background, a target spacetime is fixed, and the string perturbation series provides an S-matrix for perturbative quantum gravity on this background spacetime, encoding, if you wish, perturbative quantum fluctuations of the metric tensor...

This is not really correct, at least not in the original "canonical" LQG (maybe in some variant of CDT). The definition of LQG is to start from a Hamiltonian formulation of 3+1 dimensional gravity, then encode the field variables as SU(2)-connections, then encode these as parallel transport...

No. But, to be frank, if you are trying to advertise any insights that might be found there, you are not doing them a favor here, because they come across as really confused. I wish I knew what you are asking here, because then I would really try to help. But I fail to make sense of what you...

Absolutely. I am guessing that Vafa chose the whimsical term "swampland" precisely in order to evoke such feelings. I just wish he wouldn't associate all those sweeping conjectures now with the term. The field of string phenomenology has now had enough of whimsicalism and conjectures, what it...

Okay, in that case one can say something concrete as to the relation of such general covariant laws to Hamiltonian laws depending on time, and on the quantization in the two perspectives. Namely, this is the perspective of the "covariant phase space" in contrast to the phase space associated...