[Paper Review] The effect of rotation in the neutrino emission from a neutron star

Maxim Dvornikov, Claudio Dib|arXiv (Cornell University)|Jul 9, 2009

Neutrino Physics Research3 citations

TL;DR

This paper investigates how neutron star rotation affects neutrino emission, focusing on flavor oscillations and neutrino trapping. It finds that low-energy neutrinos can be trapped due to rotation, with only minor shifts in the MSW resonance for high-angular-momentum neutrinos, and estimates spin-down from neutrino emission at ~10% within the first few seconds of core formation.

ABSTRACT

We study the interaction of neutrinos with matter of a rotating neutron star. First we examine the effect of the rotation on neutrino flavor oscillations and possible existence of bound states of low energy neutrinos in rotating matter. Then we consider the spin-down of a star during its early stages due to the neutrino emission. We find that low energy neutrinos indeed can get trapped, although the effect my not have observable consequences. Concerning flavor oscillations, only for neutrinos emitted with high angular momentum is there a small shift in the value of the electron density for the Mikheyev-Smirnov-Wolfenstein resonance. Finally, the spin-down due to neutrino emission was estimated be to near 10 % and occurs only in the first few seconds of the core formation.

Motivation & Objective

• To understand how rotation influences neutrino flavor oscillations in neutron star matter.
• To investigate the possibility of bound states for low-energy neutrinos in rotating neutron star matter.
• To estimate the impact of neutrino emission on the spin-down of a newly formed neutron star.
• To assess whether rotational effects on neutrino processes have observable consequences.

Proposed method

• Modeling neutrino propagation in rotating neutron star matter using effective field theory and general relativistic corrections.
• Analyzing flavor oscillations via the Mikheyev-Smirnov-Wolfenstein (MSW) mechanism in rotating frames.
• Solving the Dirac equation for neutrinos in a rotating, dense medium to identify bound state conditions.
• Estimating spin-down timescale by integrating neutrino energy loss rates over the first few seconds of core collapse.
• Using the star's rotational frequency and density profile to compute angular momentum-dependent neutrino emission effects.
• Applying perturbative methods to assess small shifts in the MSW resonance condition due to rotation.

Experimental results

Research questions

• RQ1 Can low-energy neutrinos become trapped in the gravitational and rotational potential of a rotating neutron star?
• RQ2 How does rotation modify the resonance condition for neutrino flavor oscillations in the MSW effect?
• RQ3 What is the contribution of neutrino emission to the spin-down of a young neutron star during its first few seconds?
• RQ4 Are the rotational effects on neutrino processes large enough to produce observable signatures in neutrino signals?

Key findings

• Low-energy neutrinos can be trapped in the rotating neutron star due to the combined effects of gravity and rotation, though the effect may not be observationally significant.
• For neutrinos emitted with high angular momentum, rotation induces a small shift in the electron density at which the MSW resonance occurs.
• Neutrino emission contributes to spin-down of the neutron star, with a total loss of approximately 10% of its initial angular momentum in the first few seconds after core formation.
• The trapping of low-energy neutrinos is a consequence of the effective potential well created by rotation and gravity, though the trapping depth is limited.
• The shift in the MSW resonance due to rotation is small and unlikely to significantly alter neutrino flavor conversion probabilities.
• The spin-down mechanism via neutrino emission is most relevant in the early stages of neutron star evolution, particularly during the first few seconds of core formation.