On the estimation of gravitational wave spectrum from cosmic domain walls

Abstract

We revisit the production of gravitational waves from unstable domain walls analyzing their spectrum by the use of field theoretic lattice simulations with grid size 1024 3 , which is larger than the previous study. We have recognized that there exists an error in the code used in the previous study, and the correction of the error leads to the suppression of the spectrum of gravitational waves at high frequencies. The peak of the spectrum is located at the scale corresponding to the Hubble radius at the time of the decay of domain walls, and its amplitude is consistent with the naive estimation based on the quadrupole formula. Using the numerical results, the magnitude and the peak frequency of gravitational waves at the present time are estimated. It is shown that for some choices of parameters the signal of gravitational waves is strong enough to be probed in the future gravitational wave experiments.PACS numbers: 98.80.Cq, 04.30.Db Contents 15A. The coding error 15References

Piercing of domain walls: new mechanism of gravitational radiation

“…Collapsing unstable DWs generate gravitational waves, whose spectrum, sensible to particular underlying models, can be an important source of information about the early universe. In view of the forthcoming experimental studies of relict gravitational waves, this subject attracted attention recently [8][9][10][11][12][13][14], for a review see [15]. Particular models considered include the hybrid inflation [9], the standard model extended to the very early universe [14], the Higgs model [11], the next-to-minimal supersymmetric standard model [12] and some other.…”

“…For brevity, we omit an index in z RS in the rest of this section. Using the non-vanishing Christoffel symbols 10) in the geodesic equationẍ M + Γ M LRẋ LẋS = 0 one derives the following two equations t = 2kṫż sgnz,z = e −2k|z| kṫ 2 sgnz , whose solution is…”

“…Since the expected radiation power is quadratic in the amplitude which itself is the second order quantity, we will need here to keep terms up to fourth order. Denoting the third order tensor in (4.5) as N (3) M N ≡ C M N and the quatric term as N (4) M N ≡ Q M N , we will have: 10) where multiple arguments in the cubic and quatric terms indicate the order of variables in the corresponding products. Since in each order the Einstein equations read:…”

“…Squaring of (6.21) and substituting it into (6.2) leads to the integrals V D−3 2 which for D > 6 turn out to be "nonbeamed" and for D = 6 logarithmic, 12 thus taking help of (A.7) this yields: 22) with ω max discussed above (6.10). 10 The amplitude, emitted energy and radiation efficiency, corresponding to this mirror case, will be denoted with uppercase star. 11 Remarkably, the validity of the low-angle approximation is extended to the angle region of order O(1),…”

Topological defects and nano-Hz gravitational waves in aligned axion models

“…In the violent collisions of domain walls, gravitational waves are produced over frequencies ν corresponding to a typical physical length scale [61][62][63][64]. Once the domain-wall network follows the scaling law, a typical curvature radius is of order the Hubble parameter.…”