Séminaire / Seminar GReCO |
| « The cosmological constant problem and renormalization group » |
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I.L. Shapiro |
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The talk starts with an elementary introduction to the Cosmological Constant
(CC) problem. There are actually several distinct problems, one of them is that many people apply the cut-off regularization in a very naive way and misinterpret the results as a fundamental difficulty. From the other side there is a real and very difficult CC problem, which results from the existence of many independent contributions to the same small quantity, that is the CC, or, equivalently, energy density of vacuum. The real CC problem consists in the enormous precision of the requested fine-tuning for one of these contributions. The CC problem can be seen as mainly a Quantum Field Theory hierarchy-type problem, which comes from the "conflict" between the particle physics scale where we evaluate the mentioned contributions and the tiny cosmic scale where we observe their sum. The development and improvement of the methods of Quantum Field Theory in curved space-time is necessary for better understanding of the CC problem, in both early and late universe cases. In particular, there is a possibility of variable CC due to the quantum effects of matter fields, which can be described by the renormalization group running of CC in the far IR. Since our present-day knowledge of the Appelquist and Carazzone decoupling theorem in gravity is restricted, the possibility of such a running can not be theoretically proved or ruled out at the present-day state of art in the field, and this opens the door for some interesting phenomenological applications in cosmology and astrophysics. |
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lundi 19 janvier 2015 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |