On the possibility of superradiant neutrino emission by atomic condensates

TL;DR

This work investigates whether superradiant-like collective neutrino emission can emerge from ultracold atomic condensates, addressing how quantum statistics constrain cooperativity. Using a Lindblad framework with three coupled collective modes, the authors analyze three decay-statistics scenarios: boson→boson, boson→fermion, and fermionic BEC→boson. They find that Pauli blocking suppresses cooperative emission in boson→fermion channels, while a deep-BEC fermionic starting point decaying to bosons can exhibit pronounced superradiant behavior; a boson-to-boson channel remains viable under the right conditions. The results help delineate which physical systems and decay pathways could realize coherent neutrino emission, offering guidance for experimental exploration and more rigorous theoretical modeling.

Abstract

In a recent work [B. J. P. Jones and J. A. Formaggio, Phys. Rev. Lett. 135, 111801 (2025)], the possibility of superradiant neutrino emission from atomic condensates has been theoretically proposed. Subsequent analysis by Y. K. Lu, H. Lin, and W. Ketterle [arXiv:2510.21705] questioned this scenario, emphasizing the limiting role of the fermionic nature of the decayed atoms. In this study, we revisit the problem and discuss under which conditions collective emission phenomena might still emerge in cold-atom systems.

Figures (5)

• Figure 1: Plot of the decayed fraction $\frac{\braket{n_b}}{N}$, according to Eq.\ref{['nbsolution']}, for different atom populations $N$ as specified in figure legend (See Ref.Jones:2024lhf for comparison). Dashed line corresponds to the case of no superradiance.
• Figure 2: Plot of the decayed fraction $\frac{\braket{n_b}}{N}$, according to Eq.\ref{['eq:nbDynM']}, for different values of the $\eta$ parameter for fixed atom population $N=10^5$.
• Figure 3: Plot of the decayed fraction $\sum_k\braket{n_k}/N$ as a function of time, obtained from Eqs.\ref{['eq:AtomDD']} and \ref{['nkdot']} and assuming negligible density-density correlations ($\braket{n_k n_{k'}}\approx \braket{n_k}\braket{n_{k'}}$) and fast neutrino emission ($\braket{n_c}\approx 0$). Distinct curves are obtained by fixing the atom population to $N=100$ and $\alpha=80$ and considering different values of the parameter $g_\alpha/\gamma$. We set $g_\alpha = \gamma$ for upper curve (yellow), $g_\alpha = 0.1 \gamma$ for middle curve (green), $g_\alpha = 0.01 \gamma$ for lower curve (red).
• Figure 4: Schematic representation of the elementary and composite processes occurring in a deeply bound fermionic BEC undergoing electron-capture decay into a bosonic atomic species. Double gray lines denote tightly bound fermion pairs, single black lines indicate unpaired fermions, and single red lines represent bosons produced by decay. Neutrino emission, always accompanying the decay process, is omitted for clarity. The physical regime considered assumes that the recombination time of two unpaired fermions is much shorter than the decay rate, so that the transient population of unpaired fermions is effectively negligible. (a) Decay of a single fermionic constituent within a bound pair, leading to the conversion of one fermion into a boson. (b) Double decay of both fermions forming a pair, resulting in the emission of two bosons. (c) Fast pairing (recombination) of two unpaired fermions into a tightly bound pair. (d) Decay of a single unpaired fermion into a bosonic atom. (e) Decay of one bound fermion within a pair followed by the recombination of the resulting unpaired fermion with another unpaired partner, forming a new pair. (f) A boson-mediated process in which the decay of a bound fermion and the subsequent recombination events effectively lead to the emission of two bosons, with the fermionic condensate providing the intermediate virtual channel.
• Figure 5: Plot of the decayed fraction $\frac{\braket{n_b}}{N}$, according to Eq.\ref{['nbFB']}, for different atom populations $N$ as specified in figure legend.