Percolating Cosmic String Networks from Kination


Conlon, Joseph P., Copeland, Edmund J., Hardy, Edward, González, Noelia Sánchez


We describe a new mechanism, whose ingredients are realised in string compactifications, for the formation of cosmic (super)string networks. Oscillating string loops grow when their tension $\mu$ decreases with time. If $2H + \dot{\mu}/\mu < 0$, where $H$ is the Hubble parameter, loops grow faster than the scale factor and an initial population of isolated small loops (for example, produced by nucleation) can grow, percolate and form a network. This condition is satisfied for fundamental strings in the background of a kinating volume modulus rolling towards the asymptotic large volume region of moduli space. Such long kination epochs are motivated in string cosmology by both the electroweak hierarchy problem and the need to solve the overshoot problem. The tension of such a network today is set by the final vacuum; for phenomenologically appealing Large Volume Scenario (LVS) vacua, this would lead to a fundamental string network with $G \mu \sim 10^{-10}$.

  • [1] A. Vilenkin and E. P. S. Shellard, Cosmic Strings and Other Topological Defects (Cambridge University Press, 2000).
  • [2] E. J. Copeland and T. W. B. Kibble, Cosmic Strings and Superstrings, Proc. Roy. Soc. Lond. A 466, 623 (2010), arXiv:0911.1345 [hep-th].
  • [3] G. Agazie et al. (NANOGrav), The NANOGrav 15 yr Data Set: Evidence for a Gravitationalwave Background, Astrophys. J. Lett. 951, L8 (2023), arXiv:2306.16213 [astro-ph.HE].
  • [4] R. Abbott et al. (LIGO Scientific, Virgo, KAGRA), Constraints on Cosmic Strings Using Data from the Third Advanced LIGO–Virgo Observing Run, Phys. Rev. Lett. 126, 241102 (2021), arXiv:2101.12248 [gr-qc].
  • [5] T. W. B. Kibble, Topology of Cosmic Domains and Strings, J. Phys. A 9, 1387 (1976).
  • [6] M. Yamaguchi, Cosmological evolution of cosmic strings with time dependent tension, Phys. Rev. D 72, 043533 (2005), arXiv:hep-ph/0503227.
  • [7] K. Ichikawa, T. Takahashi, and M. Yamaguchi, Implications of cosmic strings with time-varying tension on CMB and large scale structure, Phys. Rev. D 74, 063526 (2006), arXiv:hep-ph/0606287.
  • [8] H.-b. Cheng and Y.-q. Liu, The Circular loop equation of a cosmic string with time-varying tension, Mod. Phys. Lett. A 23, 3023 (2008), arXiv:0801.2808 [hep-th].
  • [9] J. Sadeghi, H. M. Farahani, B. Pourhassan, and S. M. Noorbakhsh, Cosmic string in the BTZ Black Hole background with time-dependant tension, Phys. Lett. B 703, 14 (2011), arXiv:0903.0292 [hep-th].
  • [10] L.-L. Wang and H.-B. Cheng, The evolution of circular loops of a cosmic string with periodic tension, Phys. Lett. B 713, 59 (2012), arXiv:1206.2095 [hep-th].
  • [11] W. T. Emond, S. Ramazanov, and R. Samanta, Gravitational waves from melting cosmic strings, JCAP 1 (1), 57, arXiv:2108.05377 [hep-ph].
  • [12] A. M. Srivastava, Percolating cosmic string loops from evaporating primordial black holes, Phys. Lett. B 853, 138683 (2024), arXiv:2405.03736 [gr-qc].
  • [13] E. J. Copeland, T. W. B. Kibble, and D. A. Steer, The Evolution of a network of cosmic string loops, Phys. Rev. D 58, 043508 (1998), arXiv:hep-ph/9803414.
  • [14] Y. Gouttenoire, G. Servant, and P. Simakachorn, Kination cosmology from scalar fields and gravitational-wave signatures, (2021), arXiv:2111.01150 [hep-ph].
  • [15] F. Apers, J. P. Conlon, E. J. Copeland, M. Mosny, and F. Revello, String Theory and the First Half of the Universe, (2024), arXiv:2401.04064 [hep-th].
  • [16] J. P. Conlon and F. Revello, Catch-me-if-you-can: the overshoot problem and the weak/inflation hierarchy, JHEP 11, 155, arXiv:2207.00567 [hep-th].
  • [17] F. Apers, J. P. Conlon, M. Mosny, and F. Revello, Kination, meet Kasner: on the asymptotic cosmology of string compactifications, JHEP 08, 156, arXiv:2212.10293 [hep-th].
  • [18] M. Reece, Extra-Dimensional Axion Expectations, (2024), arXiv:2406.08543 [hep-ph].
  • [19] F. Marchesano and L. Melotti, EFT strings and emergence, JHEP 02, 112, arXiv:2211.01409 [hep-th].
  • [20] E. Witten, Cosmic Superstrings, Phys. Lett. B 153, 243 (1985).
  • [21] E. J. Copeland, R. C. Myers, and J. Polchinski, Cosmic F and D strings, JHEP 06, 013, arXiv:hep-th/0312067.
  • [22] M. Hindmarsh, J. Lizarraga, A. Urio, and J. Urrestilla, Loop decay in Abelian-Higgs string networks, Phys. Rev. D 104, 043519 (2021), arXiv:2103.16248 [astro-ph.CO].
  • [23] D. Matsunami, L. Pogosian, A. Saurabh, and T. Vachaspati, Decay of Cosmic String Loops Due to Particle Radiation, Phys. Rev. Lett. 122, 201301 (2019), arXiv:1903.05102 [hep-ph].
  • [24] V. Balasubramanian, P. Berglund, J. P. Conlon, and F. Quevedo, Systematics of moduli stabilisation in Calabi-Yau flux compactifications, JHEP 03, 007, arXiv:hep-th/0502058.
  • [25] R. Blumenhagen, J. P. Conlon, S. Krippendorf, S. Moster, and F. Quevedo, SUSY Breaking in Local String/F-Theory Models, JHEP 09, 007, arXiv:0906.3297 [hep-th].
  • [26] R. Basu, A. H. Guth, and A. Vilenkin, Quantum creation of topological defects during inflation, Phys. Rev. D 44, 340 (1991).