arXiv subjects

Dimitrios Toulikas

Publications and source records attributed to Dimitrios Toulikas.

12 recordsLinked to original sources

arXiv2026

Lost in Translation: Moduli Stabilization from EFT to Eleven Dimensions

We explicitly show how moduli stabilization is realized geometrically in M-theory compactified on $T^4/\mathbb{Z}_2\, \times\, $K3, by using the Gibbons-Hawking approximation of the K3 metric. By relating this compactification to certain microstate geometries, we present the explicit solutions in which fully backreacted fluxes on certain four-cycles stabilize three of the $T^4/\mathbb{Z}_2$ compactification moduli. The minimal tadpole contribution of these fluxes is linear in the number of stabilized moduli, and we argue that this linear relation holds for more general fluxes. We also construct a one-parameter family of supersymmetric eleven-dimensional solutions that break Lorentz invariance and the warped-product structure of the compactification. These solutions are a continuous deformation of the warped-product Lorentz-invariant compactification, to which they reduce when the moduli reach their stabilized values. Away from the Lorentz-invariant locus, the fluxes are no longer self-dual in the internal space, and include fields that do not exist in the corresponding EFT. Remarkably, although these fluxes still stabilize a modulus, it is not the $T^4/\mathbb{Z}_2$ modulus that appears stabilized in the Lorentz-invariant solution, but rather a nontrivial combination of the $T^4$ volume and K3 shape moduli. The existence of these solutions suggests that the EFT description of moduli stabilization can be misleading and does not reflect the moduli-stabilization dynamics of the full eleven-dimensional theory. Our results extend straightforwardly to Type IIB String Theory compactified on orientifolds of $T^2 \times K3$.

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arXiv2026

Zooming out of AdS$_4 \times$S$^2 \times$S$^2$: The Branes behind the CFT's

We reveal the supersymmetric brane configurations that give rise to AdS$_4\times$S$^2\times$S$^2$ supergravity solutions, which are holographic duals to three-dimensional $N=4$ CFTs or to conformal boundaries and domain walls of four-dimensional $N=4$ SYM. We show that these solutions preserve the same Killing spinors as orthogonal D3, D5 and NS5 branes in flat space, and that the singular sources of these solutions correspond to semi-infinite D3-D5 and D3-NS5 spikes. We track these solutions all the way from the weak-coupling regime of parameters, where the branes do not backreact, to the supergravity regime. We explain how the AdS$_4$ factor arises from certain universal self-similar bending regions of the five-branes, whose steepness is the same as the weak-coupling linking numbers. We also propose a brane configuration that gives rise to the Janus interface solutions. Our construction gives a clear geometric explanation of the Gaiotto-Witten "good-bad-ugly" classification of eight-supercharge theories: only good theories have five-branes that do not cross when back-reacting, and end up sourcing an AdS$_4\times$S$^2\times$S$^2$ solution.

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arXiv2025

Effervescent Spikes in M-theory

AdS$_3 \times$ S$^3 \times$ S$^3$ solutions warped over a Riemann surface, $Σ$, are indexed by a parameter, $γ$, that defines the superconformal algebra, $D(2,1; γ) \oplus D(2,1; γ)$ they preserve. We show that these solutions come from multiple back-reacted M2-M5 spikes, and that different values of $γ$ correspond to different scaling limits of the same M2-M5 solutions. We find that when $γ$ switches from positive to negative, the infrared region of the AdS$_3$ switches from the tip of spikes, far from the M5 branes, to the bottom of the spikes, far from the M2 branes. We also explain how the bubbling negative-$γ$ solutions emerge from the geometric transition of multiple M2-M5 spikes.

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arXiv2025

Maze Topiary in Supergravity

We show that the supergravity solutions for 1/4-BPS intersecting systems of M2 and M5 branes are completely characterized by a single ``maze'' function that satisfies a non-linear ``maze'' equation similar to the Monge-Ampère equation. We also show that the near-brane limit of certain intersections are $AdS_3 \times S^3 \times S^3$ solutions warped over a Riemann surface, $Σ$. There is an extensive literature on these subjects and we construct mappings between various approaches and use brane probes to elucidate the relationships between the M2-M5 and AdS systems. We also use dualities to map our results onto other systems of intersecting branes. This work is motivated by the recent realization that adding momentum to M2-M5 intersections gives a supermaze that can reproduce the black-hole entropy without ever developing an event horizon. We take a step in this direction by adding a certain type of momentum charges that blackens the M2-M5 intersecting branes. The near-brane limit of these solutions is a BTZ$^{extremal} \times S^3 \times S^3 \times Σ$ geometry in which the BTZ momentum is a function of the Riemann surface coordinates.

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arXiv2024

The M2-M5 Mohawk

We show that the near-brane back-reaction of M2 branes ending on M5 branes has a rich "spike structure" that is determined by partitioning the numbers of M2 branes that are terminating on groups of M5 branes. The near-brane limit of the metric describing these branes has an AdS$_3$ factor, implying the existence of a dual CFT. Each partition of the M2 and M5 charges among spikes gives rise to a different "mohawk" revealing a new layer of brane fractionation. We conjecture that all these mohawks are dual to ground states of near-brane-intersection CFT's. We show that the supergravity solutions describing these mohawks are part of the large families of AdS$_3$ $\times S^3 \times S^3$ solutions described in [arXiv:1312.5477]. We identify precisely which of these families are relevant to brane intersections and show that the AdS$_3$ invariance emerges from the self-similarity of the spikes.

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arXiv2024

Waves on Mazes

One way to describe the entropy of black holes comes from partitioning momentum charge across fractionated intersecting brane systems. Here we construct $\frac{1}{8}$-BPS solutions by adding momentum to a maze of M2-brane strips stretched between M5 branes. Before the addition of momentum, the $\frac{1}{4}$-BPS supergravity solution describing the maze is governed by a master function obeying a complicated Monge-Ampère equation. Given such a solution, we show that one can add momentum waves without modifying the $\frac{1}{4}$-BPS M2-M5 background. Remarkably, these excitations are fully determined by a layered set of $\textit{linear}$ equations. The fields responsible for carrying the momentum are parameterized by arbitrary functions of a null direction, and have exactly the same structure as in brane world-volume constructions. The fact that the momentum and flux excitations of the M2-M5-P system are governed by a linear structure brings us one step closer to using supergravity solutions to capture the entropy of supersymmetric black-holes.

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arXiv2022

Themelia: the irreducible microstructure of black holes

We argue that the fundamental "atomic objects" in string theory are themelia: extended objects that have 16 supersymmetries locally. We show that all existing smooth horizonless microstate geometries can be seen as bound states of themelia, and we conjecture that all such bound states with suitable KKM charges will give rise to microstate geometries. We also construct the most general themelion with a three-torus isometry and show that it interpolates between superstrata and the super-maze.

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arXiv2022

Smearing and Unsmearing KKLT AdS Vacua

Gaugino condensation on D-branes wrapping internal cycles gives a mechanism to stabilize the associated moduli. According to the effective field theory, this gives rise, when combined with fluxes, to supersymmetric AdS$_4$ solutions. In this paper we provide a ten-dimensional description of these vacua. We first find the supersymmetry equations for type II AdS$_4$ vacua with gaugino condensates on D-branes, in the framework of generalized complex geometry. We then solve them for type IIB compactifications with gaugino condensates on smeared D7-branes. We show that supersymmetry requires a (conformal) Calabi-Yau manifold and imaginary self-dual three-form fluxes with an additional (0,3) component. The latter is proportional to the cosmological constant, whose magnitude is determined by the expectation value of the gaugino condensate and the stabilized volume of the cycle wrapped by the branes. This confirms, qualitatively and quantitatively, the results obtained using effective field theory. We find that exponential separation between the AdS and the KK scales seems possible as long as the three-form fluxes are such that their (0,3) component is exponentially suppressed. As for the localized solution, it requires going beyond SU(3)-structure internal manifolds. Nevertheless, we show that the action can be evaluated on-shell without relying on the details of such complicated configuration. We find that no "perfect square" structure occurs, and the result is divergent. We compute the four-fermion contributions, including a counterterm, needed to cancel these divergencies.

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arXiv2022

The (amazing) Super-Maze

The entropy of the three-charge NS5-F1-P black hole in Type IIA string theory comes from the breaking of $N_1$ F1 strings into $N_1 N_5$ little strings, which become independent momentum carriers. In M theory, the little strings correspond to strips of M2 brane that connect pairs of parallel M5 branes separated along the M-theory direction. We show that if one takes into account the backreaction of the M-theory little strings on the M5 branes one obtains a maze-like structure, to which one can add momentum waves. We also show that adding momentum waves to the little strings gives rise to a momentum-carrying brane configuration -- a super-maze -- which locally preserves 16 supercharges. We therefore expect the backreaction of the super-maze to give rise to a new class of horizonless black-hole microstate solutions, which preserve the rotational symmetry of the black-hole horizon and carry $\sqrt{5/6}$ of its entropy.

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arXiv2022

Anti D3-branes and gaugino condensation

Anti-D3 branes at the bottom of warped throats, commonly used to uplift the cosmological constant in String-Theory de Sitter proposals, source a plaethora of supersymmetry-breaking fluxes, that can interact nontrivially with other ingredients of the flux compactification. In this paper we perform a complex-structure decomposition of these fluxes, and compute the effect of the (0,3) flux component on the stabilization of Kähler moduli via D7-branes gaugino condensation. This allows us to obtain a new constraint on the validity of this stabilization mechanism. This effect does not appear hard to satisfy in de Sitter construction proposals that use long warped throats, but may be problematic in proposals where the warping is small.

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arXiv2022

Bare-Bones de Sitter

We compute the supersymmetry-breaking three-form fluxes generated by the addition of anti-D3 branes at the tip of a Klebanov-Strassler throat. These fluxes give rise to nontrivial terms in the superpotential when the throat is embedded in a flux compactification. We describe these terms both from a ten-dimensional and from a four-dimensional perspective and show that, upon including Kähler-moduli stabilization, the resulting potential admits de Sitter minima. Our proposed de Sitter construction does not require additional supersymmetry-breaking (0,3) fluxes, and hence is more minimalist than the KKLT proposal.

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arXiv2022

Resolving Black-Hole Microstructure with New Momentum Carriers

All known horizonless black-hole microstate geometries correspond to brane sources that acquire a finite size, and hence break the spherical symmetry of the black hole. We construct, for the first time, solutions with zero horizon area that have the same charges as a three-charge F1-NS5-P Type-IIA black hole and preserve this spherical symmetry. The momentum of these solutions is carried by longitudinal D0-D4 density fluctuations inside the NS5-branes. We argue that these solutions should be interpreted as the long-throat limit of a family of smooth, horizonless microstate geometries, called superstrata, where such geometries degenerate. The existence of these geometries indicates that a finite-size horizon does not appear even in the singular corners of the moduli space of three-charge microstate geometries.

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