Neutron stars, ungravity, and the I-Love-Q relations

Abstract

We study neutron stars (NSs) in an ungravity (UG) inspired model. We examine the UG effects on the static properties of the selected NSs, in different mass and radius regimes, i.e., ultralow, moderate, and ultrahigh NSs, using a polytropic equation of state approach. Based on the observational data, we obtain bounds on the characteristic length and scaling dimension of the UG model. Furthermore, we obtain dynamic properties, such as inertial moment (I), Love number (Love), and quadrupole moment (Q) of a slowly rotating NS in the presence of the exterior gravity and ungravity fields. The UG model is also examined with respect to the I-Love-Q universal relation.

Gravitomagnetic tidal effects in gravitational waves from neutron star binaries

“…The universality has been linked to the emergence of self-similarity of the stars' isodensity contours [80]. Such universal relations have been analyzed for higher (gravitoelectric and -magnetic) multipoles [81][82][83][84][85], for rotational-tidal Love numbers [44,[72][73][74], for the case of rapid rotation [86,87], for dynamical configurations [88], for magnetized NSs [89], in alternative gravity theories [79,[90][91][92][93][94][95], for extreme EoSs [96], and for use in parameter estimation with binary inspiral GWs [9,81,97,98]; see [99] for a review. Regarding some of the most recent calculations of particularly λ and σ for realistic NS EoSs, we note that calculations using both the "static" [72] and "irrotational" [74] fluid assumptions show universality for λ and σ at a ∼1% level (whereas for the rotational-TLNs, [72] finds significant deviations from universality while [74] finds universality at a ∼2.5% level).…”

<italic>I-Q</italic> relation of neutron star affected by massive graviton

“…但Chakrabarti等人 [14] 进一步的研究发现, 将一些物理量做适当的无量纲化 之后, 仍然可以得到与物态方程无关的I-Q关系. 另外, 很多不同的修正引力, 例如f(R)引力、ungravity引力理 论等, 其中的I-Q关系也被计算 [15,16] , 这些修正引力中 计算出的I-Q关系都与物态方程无关. 而有些修正引力 中通过数值求得的I-Q关系图线会偏离爱因斯坦引力 中得到的图线, 通过观察这些区别, 我们也可以检验引 力理论或给出一些对修正引力的限制 [12] .…”