Tidal Love numbers of black holes and neutron stars in the presence of higher dimensions: Implications of GW170817

Abstract

We calculate the tidal Love numbers of black holes and neutron stars in the presence of higher dimensions. The perturbation equations around an arbitrary static and spherically symmetric metric for the even parity modes are presented in the context of an effective four-dimensional theory on the brane. This subsequently leads to the sought expression for the tidal Love number for black holes in the presence of extra spatial dimensions. Surprisingly, these numbers are non-zero and, more importantly, negative. We extend our method to determine the tidal Love number of neutron stars in a spacetime inheriting extra dimensions and show that, in the context of effective gravitational theory on the brane, they are smaller than in general relativity. Finally we have explicitly demonstrated that earlier constraints on the parameters inherited from higher dimensions are consistent with the bound on the tidal deformability parameter from the GW170817 event as well.

Decoding signatures of extra dimensions and estimating spin of quasars from the continuum spectrum

“…The broadened and skewed iron K-α line in the reflection spectrum of black holes [180,181], the quasi-periodic oscillations observed in the power spectrum of some black holes and neutron stars [182,183], pulsar timing arrays [184,185] and imaging the event horizon of black holes with the techniques of Very Large Baseline Interferometry (VLBI) [186][187][188], all provide independent tools to probe the strong gravity regime and hence enable us to establish/falsify/constrain several alternate gravity models. Finally, one can also probe the dynamical nature of gravitational interactions by studying the gravitational waves emanating from the mergers of binary black holes using future missions like Laser Interferometer Space Antenna [105,110,114,189]. We are presently working on the observational aspects of different alternate gravity models which we aim to report in future.…”

“…The presence of extra dimensions also affect the equation of state of a neutron star which in turn alter the tidal Love numbers measuring its deformability [106][107][108][109][110]. This can be used to impose tight constraints on the extra dimensional parameters, using for example, the GW170817 event [111][112][113][114].…”

Silhouette of M87*: A new window to peek into the world of hidden dimensions

“…Possible constraints on extra dimensions from weak field tests of gravity [37], electromagnetic observations of quasars [38][39][40], collision of binary black holes and neutron stars [20][21][22][23] and calculation of quadrupole moment [41] have already been reported. In this paper we investigate the shadow of such braneworld black holes in light of the observed silhouette of M87* by the Event Horizon Telescope collaboration.…”

Constraining extra-spatial dimensions with observations of GW170817

“…We utilize the GW170817 bounds on the quadrupolar deformation of a NS in its binary companion's tidal field [32][33][34][35][36] to constrain an important parameter of Brane-world models, namely, the brane tension λ b , which counters the influence of the negative cosmological constant of the (anti-de Sitter) bulk on the brane [20,21]. One can indeed analyze the modifications due to the presence of higher dimensions to NS tidal deformations [37] caused by a companion in a binary; for some recent works regarding modifications of tidal deformability parameter in other theories beyond general relativity, see Refs. [38,39]).…”

“…[38,39]). In particular, it was demonstrated in [37] that the tidal deformability parameter for black holes in the presence of extra dimension is non-zero and, in fact, negative, while for NSs with the same central density it is smaller than the corresponding value in general relativity. Following this result we would like to understand the modifications arising in the tidal deformation of NSs due to the presence of extra dimensions.…”