The authors study the problem of obtaining observationally favored de Sitter vacua (i.e. a positive cosmological constant) in string theory and show that standard construction (``KKLT'') fails general. Generalizing ideas from inflation to ten dimensions provides additional conditions, such these cases KKLT-construction leads stable vacua.

We describe a method for finding flux vacua of type IIB string theory in which the Gukov-Vafa-Witten superpotential is exponentially small. present an example with ${W}_{0}\ensuremath{\approx}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ on orientifold Calabi-Yau hypersurface $({h}^{1,1},{h}^{2,1})=(2,272)$, at large complex structure and weak coupling.

A bstract In the first part of this note we argue that ten dimensional consistency requirements in form a certain tadpole cancellation condition can be satisfied by KKLT type vacua IIB string theory. We explain new term non-local nature is generated dynamically once supersymmetry broken and ensures tadpole. It interpreted as stress caused restoring force stabilization mechanism exerts on volume modulus. second part, it surprisingly difficult to engineer sufficiently long warped throats...

A bstract We construct supersymmetric AdS 4 vacua of type IIB string theory in compactifications on orientifolds Calabi-Yau threefold hypersurfaces. first find explicit and quantized fluxes for which the superpotential takes form proposed by Kachru, Kallosh, Linde, Trivedi. Given very mild assumptions numerical values Pfaffians, these admit all moduli are stabilized at weak coupling. By computing high-degree Gopakumar-Vafa invariants we give strong evidence that α ′ expansion is likewise...

We construct a supersymmetric vacuum of string theory in which the magnitude energy is $<{10}^{\ensuremath{-}123}$ Planck units. The mechanism that we introduce generates well-controlled exponential hierarchy from an appropriate choice quantized parameters superpotential. Our approach provides new angle on cosmological constant problem.

We show that the strong CP problem is solved in a large class of compactifications string theory. The Peccei-Quinn mechanism solves if CP-breaking effects ultraviolet completion gravity and QCD are small compared to CP-preserving axion potential generated by low-energy instantons. characterize both classes effects. To understand quantum gravitational effects, we consider an ensemble flux type IIB theory on orientifolds Calabi-Yau hypersurfaces geometric regime, taking simple model D7-branes....

Abstract We study axion-photon couplings in compactifications of type IIB string theory. find that these are systematically suppressed compared to the inverse axion periodicity, as a result two effects. First, QED theta angle for mass eigenstates light scale set by stringy instantons on cycle supporting QED. Second, with many axions intersection matrix is sparse, making kinetic mixing weak. resulting phenomenology an ensemble 200,000 toy models constructed from Kreuzer-Skarke database up...

We introduce a method for finding flux vacua of type IIB string theory in which the superpotential is exponentially small and at same time one or more complex structure moduli are stabilized near to conifold points.

We present a vast landscape of O3/O7 orientifolds that descends from the famous set complete intersection Calabi-Yau threefolds (CICY). give distributions topological data relevant for phenomenology such as orientifold-odd Hodge numbers, D3-tadpole, and multiplicities O3 O7-planes. Somewhat surprisingly, almost all these have conifold singularities whose deformation branches are projected out by orientifolding. However, they can be resolved, so most actually descend much larger possibly new...

A bstract We argue that a new type of extremely light axion is generically present in the IIB part string theory landscape. Its mass suppressed by third power warp factor strongly warped region (Klebanov-Strassler throat), suggesting name thraxion . Our observation based on generic presence several throats sharing same 2-cycle. This cycle shrinks to zero volume at end each throat. It hence trivial homology and corresponding C 2 massive. However, warping-suppressed since, if one were cut off...

A bstract We present a method to construct the extended Kähler cone of any Calabi-Yau threefold by using Gopakumar-Vafa invariants identify all geometric phases that are related flops or Weyl reflections. In this way we obtain moduli spaces favorable hypersurfaces with h 1 , ≤ 4, including toric and non-toric phases. setting perform an explicit test Weak Gravity Conjecture count BPS states. All our examples satisfy tower/sublattice WGC, in fact they even stronger lattice WGC.

A bstract We present an efficient algorithm for computing the prepotential in compactifications of type II string theory on mirror pairs Calabi-Yau threefolds toric varieties. Applying this method, we exhibit first systematic computation genus-zero Gopakumar-Vafa invariants compact with many moduli, including examples up to 491 vector multiplets.

In this note we outline the arguments against ten-dimensional consistency of simplest types KKLT de Sitter vacua, as given in arXiv:1707.08678. We comment on parametrization proposals within four-dimensional supergravity and express our disagreement with recent criticism by authors arXiv:1808.09428.

We present a particularly simple model of axion monodromy inflation: Our is the lowest-lying KK-mode RR-2-form-potential C2 in standard Klebanov–Strassler throat. One can think this inflaton candidate as being defined by integral over S2 cycle It obtains an exponentially small mass from IR-region which shrinks to zero size. Crucially, has be shared between two throats, such that second locus where also warped region. Well-known problems like potentially dangerous back-reaction...

In flux compactifications of type IIB string theory with D3 and seven-branes, the negative induced charge localized on seven-branes leads to an apparently pathological profile metric sufficiently close source. With volume modulus stabilized in a KKLT de Sitter vacuum this region takes over significant part entire compactification, threatening spoil effective field theory. paper we employ Seiberg-Witten solution pure $SU(N)$ super Yang-Mills argue that wrapped can be thought as bound states...

We observe that racetrack models for moduli stabilization are in tension with strong forms of the Weak Gravity Conjecture (WGC). Moreover, recently, it was noted controlled KKLT-type de Sitter vacua seem to require a fine-tuning type introduced by Kallosh and Linde. combine these observations conclude quests realizing parametrically large axion decay constants intimately related. Finally, we discuss possible approaches curing conflict between scheme WGC.

A bstract We study Euclidean D3-branes wrapping divisors D in Calabi-Yau orientifold compactifications of type IIB string theory. Witten’s counting fermion zero modes terms the cohomology structure sheaf $$ {\mathcal{O}}_D <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>O</mml:mi> <mml:mi>D</mml:mi> </mml:msub> </mml:math> applies when is smooth, but we argue that effective threefolds typically have singularities along rational curves. generalize to such singular...

We study axion-photon couplings in compactifications of type IIB string theory. find that these are systematically suppressed compared to the inverse axion periodicity, as a result two effects. First, QED theta angle for mass eigenstates light scale set by stringy instantons on cycle supporting QED. Second, with many axions intersection matrix is sparse, making kinetic mixing weak. resulting phenomenology an ensemble $200{,}000$ toy models constructed from Kreuzer-Skarke database up maximum...

We show that the strong CP problem is solved in a large class of compactifications string theory. The Peccei-Quinn mechanism solves if CP-breaking effects ultraviolet completion gravity and QCD are small compared to CP-preserving axion potential generated by low-energy instantons. characterize both classes effects. To understand quantum gravitational effects, we consider an ensemble flux type IIB theory on orientifolds Calabi-Yau hypersurfaces geometric regime, taking simple model D7-branes....

We construct a vacuum of string theory in which the magnitude energy is $< 10^{-123}$ Planck units. Regrettably, sign negative, and some supersymmetry remains unbroken.

We construct compactifications of type IIB string theory that yield, at leading order in the $\alpha^\prime$ and $g_s$ expansions, de Sitter vacua form envisioned by Kachru, Kallosh, Linde, Trivedi. specify explicit Calabi-Yau orientifolds quantized fluxes for which we derive four-dimensional effective supergravity theories, incorporating exact flux superpotential, nonperturbative superpotential from Euclidean D3-branes, K\"ahler potential tree level loop expansion but to all orders...

We enumerate topologically-inequivalent compact Calabi-Yau threefold hypersurfaces. By computing arithmetic and algebraic invariants the Gopakumar-Vafa of curves, we prove that number distinct simply connected hypersurfaces resulting from triangulations four-dimensional reflexive polytopes is 4, 27, 183, 1,184 8,036 at $h^{1,1}$ = 1, 2, 3, 5, respectively. also establish there are ten equivalence classes Wall data non-simply threefolds Kreuzer-Skarke list. Finally, give a provisional count...