arXiv subjects

Ronny Frumkin

Publications and source records attributed to Ronny Frumkin.

7 recordsLinked to original sources

arXiv2026

The phase diagram of the D1-D5 CFT and localized black holes

In this paper we analyze the phases that dominate the microcanonical ensemble at various energies in the D1-D5 CFT, which is dual to type II string theory on $AdS_3 \times S^3\times T^4$. We focus on black hole solutions, and on the dependence of the phase structure on the ratio of the size of the torus to the AdS scale; as small localized black holes (with horizon topology $S^8$) grow, they can start to fill the $S^3$ or the $T^4$ or both, and we analyze the general aspects of the transitions between the various phases of uniform and non-uniform black holes, incorporating known solutions and discussing the properties of additional unknown solutions. Some features of the transitions between these phases are similar to higher dimensional AdS spaces, while other features are different. We provide evidence that when the torus is much larger than the AdS radius, there is a large range of energies where the typical states are a novel phase, described by a lattice (in the $T^4$ directions) of black holes with horizon topology $S^5\times S^3$. In this phase the entropy is linear in the energy, with a coefficient that is of order the AdS radius.

hep-th↗

arXiv2025

Large N Chern-Simons-matter fixed points with multiple flavors

In this paper we analyze the $2+1$d conformal fixed points arising from $SU(N_c)$ Chern-Simons-matter theories with multiple flavors $N_f > 1$ in the 't Hooft large $N_c$ limit. The multi-flavor generalization of quasi-fermionic theories (fermions or critical scalars coupled to Chern-Simons gauge fields) is straightforward, but this is not true for quasi-bosonic theories (scalars or critical fermions coupled to Chern-Simons gauge fields). The latter theories have three flavor-singlet relevant operators and also three marginal operators, that become exactly marginal for infinite $N_c$, but have a non-zero beta function at order $1/N_c$. We compute the beta functions of these couplings in various weak coupling limits, and discuss also their general structure, generalizing previous computations for $N_f=1$. We find that IR-stable fixed points of the marginal couplings exist for some values of $N_f$ and of the 't Hooft coupling $\lambda$, but not for other values, and in one case we can explicitly follow how two pairs of fixed points merge and disappear as $\lambda$ is increased. We also analyze the ``Semi-Critical'' conformal field theories that arise when fine-tuning two (rather than three) relevant operators, and compute the beta function for their (single) marginal coupling constant.

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arXiv2025

Inelastically Decoupling Dark Matter

We present a new dark matter candidate, the `inELastically DEcoupling Relic' (iELDER), which is a cold thermal relic whose abundance is determined by the freeze out of its inelastic scattering off of bath particles in the presence of $3\to2$ self-annihilations. The dark matter is predicted to be light, in the $O(\mathrm{MeV}-\mathrm{GeV})$ range, with significant self-annihilations and very weak inelastic couplings to ordinary matter. We demonstrate iELDER dark matter using a $Z_3$-symmetric toy model as well as QCD-like pion theories-the latter showing promising prospects for detection and providing a new benchmark for future searches.

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arXiv2025

Phases of Dark Matter from Inverse Decays

Inverse decays are an interesting avenue for producing dark matter in the early universe. We study in detail various phases of dark matter parameter space where inverse decays control its abundance, expanding on our work of INDY dark matter and going beyond. The role of initial conditions and the impact of departure from kinetic equilibrium are investigated as well. We show how these inverse decay phases can arise in theories of a kinetically mixed dark photon and dark Higgs, with promising prospects for detection at upcoming experiments.

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arXiv2024

Twisted times, the Schwarzian and its deformations in DSSYK

The IR dynamics of SYK is that of the Schwarzian theory, the effective theory of broken reparametrization invariance. In the double scaling limit, SYK is completely solvable by chord diagrams, whose generating functional is a bilocal Liouville theory. At low temperatures a set of modes in this description becomes soft. We interpret them as reparametrization of some twisted time coordinates, and show explicitly that they lead to the nonlinear Schwarzian theory. We further consider deformations of the theory in the double scaling limit, giving rise to diagrams with multiple species of chords, and show that the generating functional is now a Liouville theory with multiple fields. These deformations can be tracked to the IR and we discuss how they affect the Schwarzian.

hep-th↗

arXiv2022

Roadmap to Thermal Dark Matter Beyond the WIMP Unitarity Bound

We study the general properties of the freezeout of a thermal relic. We give analytic estimates of the relic abundance for an arbitrary freezeout process, showing when instantaneous freezeout is appropriate and how it can be corrected when freezeout is slow. This is used to generalize the relationship between the dark mater mass and coupling that matches the observed abundance. The result encompasses well-studied particular examples, such as WIMPs, SIMPs, coannihilation, coscattering, inverse decays, and forbidden channels, and generalizes beyond them. In turn, this gives an approximate perturbative unitarity bound on the dark matter mass for an arbitrary thermal freezeout process. We show that going beyond the maximal masses allowed for freezeout via dark matter self-annihilations (WIMP-like, $m_{\rm DM}\gg\mathcal{O}(100~\rm TeV)$) predicts that there are nearly degenerate states with the dark matter and that the dark matter is generically metastable. We show how freezeout of a thermal relic may allow for dark matter masses up to the Planck scale.

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arXiv2021

Thermal Dark Matter from Freezeout of Inverse Decays

We propose a new thermal dark matter candidate whose abundance is determined by the freezeout of inverse decays. The relic abundance depends parametrically only on a decay width, while matching the observed value requires that the coupling determining the width-and the width itself-should be exponentially small. The dark matter is therefore very weakly coupled to the Standard Model, evading conventional searches. This INverse DecaY ('INDY') dark matter can be discovered by searching for the long-lived particle that decays into the dark matter at future planned experiments.

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