Can baby universe absorption explain dark energy?

It has been proposed that the accelerated expansion of the Universe can be explained by the merging of our Universe with baby universes, resulting in dark energy with a phantomlike equation of state. However, the evidence in favor of it did not include the full set of cosmological observables. Here we examine the implications of this model for both early and late universe cosmology using data from Planck collaboration, DESI 2024 and other experiments. We find that the pure baby universe model gives a poor fit to current data. Extending it to include a contribution from the cosmological constant, we find two allowed regions of parameter space: one close to <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi mathvariant="normal">Λ</a:mi><a:mi>CDM</a:mi></a:math>, and another with <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mi mathvariant="normal">Λ</d:mi><d:mo>&lt;</d:mo><d:mn>0</d:mn></d:math> plus the exotic dark energy component. The two regions can be significantly favored over <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi mathvariant="normal">Λ</g:mi><g:mi>CDM</g:mi></g:math>, depending on the choice of supernova datasets, and they can ameliorate the Hubble tension to the level of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mn>2</j:mn><j:mi>σ</j:mi></j:math>, depending on the supernova dataset. The model with <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mi mathvariant="normal">Λ</l:mi><l:mo>&lt;</l:mo><l:mn>0</l:mn></l:math> features an equation of state <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>w</o:mi><o:mo stretchy="false">(</o:mo><o:mi>a</o:mi><o:mo stretchy="false">)</o:mo></o:math> with a pole singularity at early times.