When Worlds Collide

Spencer Chang, Matthew Kleban, Thomas S. Levi

    Research output: Contribution to journalArticlepeer-review


    We analyze the cosmological signatures visible to an observer in a Coleman-de Luccia bubble when another such bubble collides with it. We use a gluing procedure to generalize the results of Freivogel, Horowitz and Shenker to the case of a general cosmological constant in each bubble and study the resulting spacetimes. The collision breaks the isotropy and homogeneity of the bubble universe and provides a cosmological 'axis of evil' which can affect the cosmic microwave background in several unique and potentially detectable ways. Unlike more conventional perturbations to the inflationary initial state, these signatures can survive even relatively long periods of inflation. In addition, we find that for a given collision the observers in the bubble with smaller cosmological constant are safest from collisions with domain walls, possibly providing another anthropic selection principle for small positive vacuum energy.

    Original languageEnglish (US)
    Article number034
    JournalJournal of Cosmology and Astroparticle Physics
    Issue number4
    StatePublished - 2008


    • cosmic strings
    • cosmological phase transitions
    • domain walls
    • inflation
    • monopoles
    • string theory and cosmology

    ASJC Scopus subject areas

    • Astronomy and Astrophysics


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