Can we live in a baby universe formed by a delayed first-order phase transition?

We examine the idea that our Universe began as a baby universe and show that this is feasible in a gauged <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>U</a:mi> <a:mo stretchy="false">(</a:mo> <a:mn>1</a:mn> <a:msub> <a:mo stretchy="false">)</a:mo> <a:mrow> <a:mi>B</a:mi> <a:mo>−</a:mo> <a:mi>L</a:mi> </a:mrow> </a:msub> </a:math> extension of the Standard Model with the classically conformal principle. For the first time, we define a measure to describe the probability that we reside in a baby universe, and find that it can be close to 1 in a considerable portion of the parameter space. The framework is consistent with current cosmological data, and it predicts the existence of a heavy neutral gauge boson, which could be detected at colliders, thereby offering a direct link between early universe dynamics and experimentally testable signatures at the TeV scale.