DEVELOPPEMENT MATHEMATIQUE ET APPLICATIONS DE LA GRAVITATION QUANTIQUE A BOUCLES. Thesis (PDF Available) · January. Des chercheurs de l’Institut Périmètre travaillent activement sur un certain nombre d’approches de ce problème, dont la gravitation quantique à boucles, les . 19 avr. A quantum theory of gravitation aims at describing the gravitational La gravité quantique à boucles étant toujours une théorie en cours de.

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At a distance it is a smooth curved two-dimensional surface, but on closer inspection we see that it is actually composed of thousands of one-dimensional linked threads. This quantity is important in the final formula for the area spectrum.

Now let us go back to the loop representation. It is possible to derive, from the covariant formulation of full quantum theory Spinfoam the correct relation between energy and area 1st lawthe Unruh temperature and the distribution that yields Hawking entropy. The second aspect of this work focuses on the physics of sub-systems and especially the physics of their boundary. So one always has. Instead one expects that one may recover a kind of semiclassical limit or weak field limit where something like “gravitons” will show up again.

Hamiltonian constraint gravitafion LQG. It is an invertible function that maps one differentiable manifold to quantiue, such that both the function and its inverse are smooth. Il y a des grandes choses que ggravitation le connaissiez.

Gravitation quantique a boucles by Podcast Science – Listen to music

Salut tous le monde Johan: The kinematic inner product structure is easily employed to provide the inner product structure after solving this first constraint; the new inner product is simply. Modern Physics 5th ed. Actually, this is what is realized in the LQG derivation of black hole entropy, and can be seen as a consequence of its background-independence — the classical black hole spacetime comes about from the semiclassical limit of the quantum state of the gravitational field, but there are many quantum states that have the same grzvitation limit.

The issue of background independence in LQG still has some unresolved subtleties. An alternative criticism is that general relativity may be gravitatikn effective field theoryand therefore quantization ignores the fundamental degrees of freedom.

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Also, obviously as any quantity Poisson commutes with itself, and the master constraint being a single constraint, it satisfies. We now consider Wilson loops with intersections. Loop Quantum Gravity has nothing to say about the matter fermions in the universe. Because of its significance this is known as the master equation.

Then different boundary dynamics are studied, both in the isolated and open cases, which shed lights again on the fundamental dynamics. An oversight in the application of the no-hair theorem is quantuque assumption that the relevant degrees of freedom accounting for the entropy of the black hole must be classical in nature; what if they were purely quantum mechanical instead and had non-zero entropy?

Without the implementation and solution of the Hamiltonian constraint no progress can be made and no reliable predictions are possible. The most well-developed applies to cosmology, called loop quantum cosmology LQCthe study of the early universe and the physics of the Big Bang. Have you forgotten your login?

Thiemann’s master constraint should not be confused with the master equation which has to do with random processes.


The reason is that the rescaled Hamiltonian constraint is a scalar density of weight two while it can be shown that only scalar densities of weight one have a chance to result in a well defined operator. It shows that spinfoam gravity can be derived from a classical action, with spinors as the fundamental configuration variables.

This thesis analyzes this problem in loop quantum gravity with tools borrowed from quantum information theory. Because of their resemblance to soap foams and the way they are labeled John Baez gave these ‘quantum space-times’ the name ‘spin foams’. Probed at a macroscopic scale, it appears as a three-dimensional continuous metric geometry. Monday, March 3, – 5: Bosonic string theory M-theory Supergravity Superstring theory.

In LQG this aspect of general relativity is taken seriously and this symmetry is preserved by requiring that the physical states remain invariant under the generators of diffeomorphisms. Faut dire que le sujet est assez motivant.

This is what Einstein discovered: With analogy to the Fourier integral given above, this generalized projector can formally be written as. The popular and technical literature makes extensive references to LQG-related topic of loop quantum cosmology. However, this is non-polynomial and the whole virtue of the complex variables is questioned. Lessons for quantum gravity”. This is not guaranteed because of a feature of quantum field theories which is that they have different sectors, these are analogous to the different phases that come about in the thermodynamical limit of statistical systems.


The canonical approach seeks to solve the Wheeler–DeWitt equation and find the physical states of the theory. Since the action is a polynomial in the spinors, canonical quantisation is straightforward.

Of particular importance is the Poisson bracket algebra formed between the smeared constraints themselves as it completely determines the theory. But problems similar to using the metric formulation arise when one tries to quantize the theory.

Loop quantum gravity Wheeler—DeWitt equation.

Contrary to this, LQG is based only on quantum theory and general relativity and its scope is limited to understanding the quantum aspects of the gravitational interaction.

Tuesday, November 28, – Just as imposing the classical simplicity constraint recovers general relativity gravittation BF theory, one expects an appropriate quantum simplicity constraint will recover quantum gravity from quantum BF theory.

Since LQG has been formulated in 4 dimensions with and without supersymmetryand M-theory requires supersymmetry and 11 dimensions, a direct comparison between the two has not been possible. LQG is formally background graivtation.

Much progress has been made with regard to this issue by Engle, Pereira, and Rovelli houcles and Freidel and Krasnov [20] in defining spin foam interaction amplitudes with much better behaviour.

Retranscription: la gravité quantique à boucles – Podcast Science

Simulated Large Hadron Collider CMS particle detector data depicting a Higgs boson produced by colliding protons decaying into hadron jets and electrons. Donc, euh, faudrait que je… NicoTupe: We analyze the proposal of reconstructing geometry from correlations. Grxvitation, they are expected to give rise to space and time at distances which are large compared to the Planck length.

It competes with string theory that begins with quantum field theory and adds gravity.

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