Quantum Gravity

My research has always trodden the classical realms of General Relativity. As a result, my knowledge of advanced quantum field theories is shaky to say the least. Not that i wasn’t interested in foundational questions or in the quest for unification, or that i didn’t read something about those issues. Now i’d like to learn a bit more.

I’ve always found the fixed-background approach taken by QFT and (to my limited knowledge) String theory at odds with General Relativity’s spirit. In my opinion, gravitation is not just another force to be quantized, but rather a description of the background were other forces live in geometrical terms. If anything is to be quantized to obtain quantum gravity, it’s geometry. And since we seem to live in a world where every relevant quantity is discrete, the idea of a granular structure of space-time itself is, to me, all but natural. Although i read (without really understanding) that String theory predicts a quantized, relational space-time, the repeated affirmations of people like Witten about our not yet (?) understanding M-theory, together with the dismal multiverse speculations i’ve read recently (Lee Smolin explains exactly how i feel about it), have turned my attention, again, to Loop Quantum Gravity as an appealing subject of study. These days, i’ve been skimming several introductory and review articles, including the delicious Quantum Gravity Seminar by John Baez, and Smolin’s PI Course. The latter will be specially useful when my copy of Rovelli’s Quantum Gravity arrives in a couple of weeks, which will be about time to start studying LQG seriously, most probably guided by Christine Dantas’ excellent reading list on the subject.

Roger PenroseIn the meantime, i plan to end Roger Penrose’s The Road to Reality, which i’m sure i don’t need to review for you. In my case, this amazing book is being an excellent way of reviewing and relearning a lot of stuff i was supposed to know from the old times, and then discovering a lot of new things. I respect Penrose opinions immensely, and after seeing these recent lectures (half-way the page), i’m specially curious about his critiques of both String theory and Loop Quantum Gravity.

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