Fluxbrane inflation

Abstract

As a first step towards inflation in genuinely F-theoretic setups, we propose a scenario where the inflaton is the relative position of two 7-branes on holomorphic 4-cycles. Non-supersymmetric gauge flux induces an attractive inter-brane potential. The latter is sufficiently flat in the supergravity regime of large volume moduli. Thus, in contrast to brane-antibrane inflation, fluxbrane inflation does not require warping. We calculate the inflaton potential both in the supergravity approximation and via an open-string oneloop computation on toroidal backgrounds. This leads us to propose a generalisation to genuine Calabi-Yau manifolds. We also comment on competing F -term effects. The end of inflation is marked by the condensation of tachyonic recombination fields between the 7-branes, triggering the formation of a bound state described as a stable extension along the 7-brane divisor. Hence our model fits in the framework of hybrid D-term inflation. We work out the main phenomenological properties of our D-term inflaton potential. In particular, our scenario of D7/D7 inflation avoids the familiar observational constraints associated with cosmic strings.

Inflation and String Theory

“…We present a number of interrelated perspectives on the potential energy of a D3-brane in a warped flux compactification, and then discuss the challenge of achieving slow-roll behavior in this setup. In §5.2, we study a few examples of brane inflation in unwarped compactifications, including D3/D7 inflation [609][610][611][612][613], fluxbrane inflation [614,615] and M5-brane inflation [616,617]. In §5.3, we discuss relativistic brane motion as a source of non-slow-roll inflation.…”

“…As explained in §4.2, the effect of compactification is to make the interaction potential for the branes be of the same order as the vacuum energy, ruining the favorable hierarchy obtained by taking the branes to be noncompact. More recently, the relative position of two D7-branes has been proposed as an inflationary direction [614,615]. Consider type IIB string theory compactified on an O3/O7 orientifold of a Calabi-Yau three-fold X 6 .…”

“…24 Because a key part of the inflaton potential arises from worldvolume flux, this scenario is called fluxbrane inflation. [614,615], the inflaton coordinate is the effective separation of a pair of intersecting D7-branes (figure adapted from [614]). …”

“…Although the similarities to D3/D7 inflation are apparent, several distinctive features of fluxbrane inflation were identified in [614]. First of all, the D7/D7 interaction potential due to flux can be made flat enough for inflation, evading the well-known difficulty [515] of achieving a sufficiently flat Coulomb interaction within an unwarped compact space.…”

“…Moduli stabilization in the type IIB orientifold (and F-theory) context is comparatively well understood, so detailed study of the moduli potential is possible. Careful investigations of this issue appear in [614,615], but the issue is not yet settled.…”