Quarkyonic matter suppresses neutron-star g modes and reverses their mass trend
Abstract
Gravity (g) modes are the only neutron-star oscillations that report on the composition of dense matter rather than on its stiffness, and work on hybrid stars has established that a first-order quark transition raises their frequency. Quarkyonic matter does the opposite. Quark-nucleon chemical equilibrium is maintained by the strong interaction, so the quarks acquire no thermodynamic freedom on an oscillation period and cs2−ce2 reduces to a positive-definite quadratic form in the lepton gradients alone. The nucleon momentum shell stiffens both sound speeds together instead of separating them, so the buoyancy factor collapses by a factor of 9.5 to 19 at an early transition and the core is left only weakly stratified. Solving the l=2 relativistic Cowling problem for ten equations of state that share one isoscalar sector, seven quarkyonic and three nucleonic controls at matched symmetry-energy slope, we found the g-mode confined to the nucleonic shell outside the core, with the horizontal flow that it lives on excluded from the core while the core is displaced almost rigidly. Its frequency falls from 158-522 Hz across the controls to 81−254~Hz across the quarkyonic models, and by 14\% at 1.4M⊙ for the matched pair at L=50mev; more important than the shift, it decreases with mass where the controls rise. Writing each frequency as the dynamical frequency (GM/R3)1/2 times a dimensionless remainder separates structure from composition. The f and p1 trends prove to be inherited from the mass--radius relation; the g1 remainder, constant to 2−9% along a nucleonic sequence, falls by a quarter to a third along a quarkyonic one and departs by a factor of two from the nucleonic g-mode relation at fixed compactness and L/K0. These are Cowling values, lower bounds at the ten-per-cent level, and the sign of the trend survives a correction of that size.
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BibTeX
@misc{kalita2026quarkyonic,
title = {{Quarkyonic matter suppresses neutron-star $g$ modes and reverses their mass trend}},
author = {Probit J Kalita and Bharat Kumar},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25175},
eprint = {2609.25175},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25175},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Quarkyonic matter suppresses neutron-star g modes and reverses their mass trend
AU - Probit J Kalita
AU - Bharat Kumar
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.25175
UR - https://arxiv.org/abs/2609.25175
AB - Gravity (g) modes are the only neutron-star oscillations that report on the composition of dense matter rather than on its stiffness, and work on hybrid stars has established that a first-order quark transition raises their frequency. Quarkyonic matter does the opposite. Quark-nucleon chemical equilibrium is maintained by the strong interaction, so the quarks acquire no thermodynamic freedom on an oscillation period and c_s^2−c_e^2 reduces to a positive-definite quadratic form in the lepton gradients alone. The nucleon momentum shell stiffens both sound speeds together instead of separating them, so the buoyancy factor collapses by a factor of 9.5 to 19 at an early transition and the core is left only weakly stratified. Solving the l=2 relativistic Cowling problem for ten equations of state that share one isoscalar sector, seven quarkyonic and three nucleonic controls at matched symmetry-energy slope, we found the g-mode confined to the nucleonic shell outside the core, with the horizontal flow that it lives on excluded from the core while the core is displaced almost rigidly. Its frequency falls from 158-522 Hz across the controls to 81−254~Hz across the quarkyonic models, and by 14\% at 1.4M_⊙ for the matched pair at L=50mev; more important than the shift, it decreases with mass where the controls rise. Writing each frequency as the dynamical frequency (GM/R^3)^1/2 times a dimensionless remainder separates structure from composition. The f and p_1 trends prove to be inherited from the mass--radius relation; the g_1 remainder, constant to 2−9% along a nucleonic sequence, falls by a quarter to a third along a quarkyonic one and departs by a factor of two from the nucleonic g-mode relation at fixed compactness and L/K_0. These are Cowling values, lower bounds at the ten-per-cent level, and the sign of the trend survives a correction of that size.
ER -