Unified Superfluid Dark Sector
Elisa G. M. Ferreira
Abstract In this talk I present a new model of a unified dark sector, where late-time
cosmic acceleration emerges from the dark matter (DM) superfluid framework. We
will start by reviewing the dark matter superfluid model and show how it describes
the dynamics of DM in large and small scales. Then we will show that if the
superfluid consists of a mixture of two distinguishable states with a small energy
gap, such as the ground state and an excited state of DM, interacting through a
contact interaction a new dynamics of late-time accelerated expansion emerges in
this system, without the need of dark energy, coming from a universe containing
only this two-state DM superfluid. I will show the expansion history and growth
of linear perturbations, and show that the difference in the predicted growth rate in
comparison to ΛCDM is significant at late times.
Keywords Superfluid dark matter · Unification
1 Introduction
Our concordance model, the ΛCDM model, exhibits an outstanding agreement
with current large scale cosmological observations [1–3]. In this model the present
accelerated expansion is described by a cosmological constant, and the dark matter
(DM) is described in the hydrodynamical limit as a fluid with negligible pressure
and sound speed, with, at most, very weakly interaction with baryonic matter,
the Cold Dark Matter (CDM). However, this simple coarse grained description
of those components presents some challenges. The cosmological constant is
Invited talk at the “XI Symposium Quantum Theory and Symmetry” (QTS-XI), Montreal, QC,
Canada, July 2019.
E. G. M. Ferreira ()
Max-Planck-Institute for Astrophysics, Garching, Germany
e-mail: elisagmf@mpa-garching.mpg.de
© Springer Nature Switzerland AG 2021
M. B. Paranjape et al. (eds.), Quantum Theory and Symmetries, CRM Series in
Mathematical Physics, https://doi.org/10.1007/978-3-030-55777-5_40
437
Elisa G. M. Ferreira
Abstract In this talk I present a new model of a unified dark sector, where late-time
cosmic acceleration emerges from the dark matter (DM) superfluid framework. We
will start by reviewing the dark matter superfluid model and show how it describes
the dynamics of DM in large and small scales. Then we will show that if the
superfluid consists of a mixture of two distinguishable states with a small energy
gap, such as the ground state and an excited state of DM, interacting through a
contact interaction a new dynamics of late-time accelerated expansion emerges in
this system, without the need of dark energy, coming from a universe containing
only this two-state DM superfluid. I will show the expansion history and growth
of linear perturbations, and show that the difference in the predicted growth rate in
comparison to ΛCDM is significant at late times.
Keywords Superfluid dark matter · Unification
1 Introduction
Our concordance model, the ΛCDM model, exhibits an outstanding agreement
with current large scale cosmological observations [1–3]. In this model the present
accelerated expansion is described by a cosmological constant, and the dark matter
(DM) is described in the hydrodynamical limit as a fluid with negligible pressure
and sound speed, with, at most, very weakly interaction with baryonic matter,
the Cold Dark Matter (CDM). However, this simple coarse grained description
of those components presents some challenges. The cosmological constant is
Invited talk at the “XI Symposium Quantum Theory and Symmetry” (QTS-XI), Montreal, QC,
Canada, July 2019.
E. G. M. Ferreira ()
Max-Planck-Institute for Astrophysics, Garching, Germany
e-mail: elisagmf@mpa-garching.mpg.de
© Springer Nature Switzerland AG 2021
M. B. Paranjape et al. (eds.), Quantum Theory and Symmetries, CRM Series in
Mathematical Physics, https://doi.org/10.1007/978-3-030-55777-5_40
437