Tilted Lemaître Model and the Dark Flow

Abstract

In the last years, the peculiar velocities of many X-ray galaxies clusters with respect to the distance have been measured directly in the rest frame of the cosmic microwave background radiation (CBR), using the kinematic Sunyaev-Zeldovich (kSZ) effect. These measures prove that exists a highly coherent motion, extending out to at least to 1 Gpc, of the matter rest frame with respect to the CBR rest frame. This global motion was named "dark flow". By using an inhomogeneous spherically symmetric "tilted" Lemaître model, we could explain the dark flow if we assume a linear increase with distance of the peculiar velocities, which is in principle allowed by these observations. This linear increase of the dark flow with the distance has the same behavior that the intrinsic dipole, due to the kinematic acceleration, which appears in the Hubble law of the Lemaître model. In the "tilted" Lemaître model considered, we consider that the radiation orthogonal congruence is a perfect fluid and the matter "tilted" congruence is an imperfect fluid with heat flux. Tilted cosmological modelsIn cosmology it is essential to specify the set of observers, or rather, the congruences of world-lines from which observations are made.Cosmological quantities depend on the choice of these congruences, specified by 4-velocities fields. For instance, with the same spacetime metric, one can have two different stress-energy-momentum tensors, corresponding to two different congru-

The Gibbs Paradox, the Landauer Principle and the Irreversibility Associated with Tilted Observers

“…The same phenomenon appears in the tilted versions of the Lemaitre-Tolman-Bondi (LTB) [13][14][15] (see [16]), the Szekeres spacetimes [17,18] (see [19]), and in many other circumstances (see [20][21][22][23][24][25] and references therein) .…”

Landauer Principle and General Relativity

“…More specifically, we have in mind the case when one of the congruences corresponds to comoving with the fluid observers, and the other is obtained by a Lorentz boost of the latter, the so called "tilted" congruence. This issue has been extensively discussed in the literature (see References [27][28][29][30][31][32][33][34][35][36][37][38][39][40] and references therein). An important point has to be stressed here: while it is true that comoving and tilted congruences are related by a Lorentz boost, the important point to keep in mind is that the comoving observer is essentially different from the tilted one in that the former assigns a specific value to the three-velocity of any fluid element (0), leading to the obvious fact that the number of degrees of freedom is lesser than in the tilted congruence.…”

Maxwell’s Demon and the Problem of Observers in General Relativity

“…The strange fact then appears that systems that are isentropic for comoving observers may become dissipative for tilted observers (see [1][2][3][4][5][6][7][8][9][10] and references therein).…”