Dipole cosmology: the Copernican paradigm beyond FLRW

Abstract

We introduce the dipole cosmological principle, the idea that the Universe is a maximally Copernican cosmology, compatible with a cosmic flow. It serves as the most symmetric paradigm that generalizes the FLRW ansatz, in light of the increasingly numerous (but still tentative) hints that have emerged in the last two decades for a non-kinematic component in the CMB dipole. Einstein equations in our “dipole cosmology” are still ordinary differential equations — but instead of the two Friedmann equations, now we have four. The two new functions can be viewed as an anisotropic scale factor that breaks the isotropy group from SO(3) to U(1), and a “tilt” that captures the cosmic flow velocity. The result is an axially isotropic, tilted Bianchi V/VII_h cosmology. We assess the possibility of model building within the dipole cosmology paradigm, and discuss the dynamics of expansion rate, anisotropic shear and tilt, in various examples. A key observation is that the cosmic flow (tilt) can grow even while the anisotropy (shear) dies down. Remarkably, this can happen even in an era of late time acceleration.

Large-Scale Asymmetry in the Distribution of Galaxy Spin Directions—Analysis and Reproduction

“…These theories include contraction prior to inflation [40], spinor-driven inflation [41], moving dark energy [42], primordial anisotropic vacuum pressure [43], spin foam cosmology [44,45], multiple vacua [46], inhomogeneous Big Bang singularity [47], cosmological big bounce [48], double inflation [49], ellipsoidal universe [8,[50][51][52][53], longitudinal gravitational wave cosmology [54], anisotropic dark energy [18,19], or rotating universe [55][56][57][58][59][60][61]. Dipole cosmological models that are based on the ΛCDM cosmology expanded to support a dipole universe [62] and a dipole big bang [63] were also proposed.…”

Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions

“…These theories include contraction prior to inflation (Piao et al, 2004), spinor-driven inflation (Bohmer and Mota, 2008), moving dark energy (Jiménez and Maroto, 2007), primordial anisotropic vacuum pressure (Rodrigues, 2008), spin foam cosmology (Rovelli and Vidotto, 2010;Kisielowski et al, 2012), multiple vacua (Piao, 2005), inhomogeneous Big Bang singularity (Schneider and Celerier, 1999), cosmological big bounce (Battisti and Marciano, 2010), double inflation (Feng and Zhang, 2003), ellipsoidal universe (Campanelli et al, 2006(Campanelli et al, , 2007(Campanelli et al, , 2011Gruppuso, 2007;Cea, 2014), longitudinal gravitational wave cosmology (Mol, 2011), anisotropic dark energy (Adhav et al, 2011;Adhav, 2011), or rotating universe (Gödel, 1949;Ozsváth and Schücking, 1962;Ozsvath and Schücking, 2001;Sivaram and Arun, 2012;Chechin, 2016;Seshavatharam and Lakshminarayana, 2020a;Campanelli, 2021). Dipole cosmological models that are based on the ΛCDM cosmology expanded to support a dipole universe (Krishnan et al, 2023) and a dipole big bang (Allahyari et al, 2023) were also proposed.…”

De Sitter-like configurations with asymptotic quintessence environment

“…where the functions, Φ(r) and M(r), are related to the gravitational Newtonian potential and to the total mass generating the solution, respectively. Consequently, deforming equation (4) with ϕ implies that the potential is changed by virtue of thermal energy associated with the field. In other words, a possible deformation, that gives rise to equation ( 3), occurs when the potential and mass change according to…”

“…Examples of anisotropic dark energy models have been explored, for instance, through Bianchi metrics and acquired recently more emphasis in view of current developments that seem to indicate, although very slightly, departures from the genuine cosmological principle, see e.g. [2][3][4]86]. Clearly, quintessence is isotropic, so demanding to violate isotropy cannot work to get a quintessence asymptotic domain.…”

“…Alternatives that aim at violating it are also possible, see e.g. [2][3][4]. 8 For the sake of completeness, it is remarkable to emphasize a significant distinction between the microphysics of dark energy and Λ.…”