# Can MONDian vector theories explain the cosmic speed up ?

## TL;DR

This paper explores whether generalized Einstein-Aether vector field models, designed to replicate MOND on galactic scales, can also account for cosmic acceleration by fitting supernova data, potentially unifying dark matter and dark energy.

## Contribution

It introduces a method to derive vector field Lagrangians from the MOND interpolating function and tests their viability for explaining cosmic acceleration.

## Key findings

- Models fit low-redshift supernova data well.
- Some tension exists at high redshift.
- Potential for a unified dark matter and dark energy framework.

## Abstract

Generalized Einstein - Aether vector field models have been shown to provide, in the weak field regime, modifications to gravity which can be reconciled with the successfull MOND proposal. Very little is known, however, on the function F(K) defining the vector field Lagrangian so that an analysis of the viability of such theories at the cosmological scales has never been performed. As a first step along this route, we rely on the relation between F(K) and the MOND interpolating function $\mu(a/a_0)$ to assign the vector field Lagrangian thus obtaining what we refer to as "MONDian vector models". Since they are able by construction to recover the MOND successes on galaxy scales, we investigate whether they can also drive the observed accelerated expansion by fitting the models to the Type Ia Supernovae data. Should be this the case, we have a unified framework where both dark energy and dark matter can be seen as different manifestations of a single vector field. It turns out that both MONDian vector models are able to well fit the low redshift data on Type Ia Supernovae, while some tension could be present in the high z regime.