Baryon and Dark Matter Genesis from Strongly Coupled Strings

TL;DR

This work proposes a UV-complete string-theory mechanism for the concurrent origin of the baryon asymmetry and dark matter abundance, leveraging strongly coupled D3-brane probes near E-type Yukawa points in F-theory GUTs. The heavy mediators between the visible sector and a light, GUT-singlet hidden sector decay in a way that generates comparable baryon and dark matter yields; strong coupling naturally provides a generational structure via towers of dyonic string junctions, enabling CP violation. A monodromic seesaw creates a hierarchical spectrum with $M_{med}\sim M_{CFT}$ and lighter $3-7_{hid}$ states, while kinetic mixing between visible and hidden $U(1)$ gauge groups depletes the symmetric DM component, yielding $m_{DM}\sim 10\,\mathrm{GeV}$. The relic abundances and mass are controlled by the conformal-symmetry-breaking scale $M_{CFT}\sim 10^{9}-10^{13}$ GeV, with the exact relation set by the visible-sector brane configuration; a correlated cosmological timeline accommodates washout, sphalerons, and potential dilution mechanisms. The scenario predicts observable signatures from kinetic/magnetic mixing and dark-sector dynamics, offering a distinctive string-based route to the observed matter content of the universe.

Abstract

D3-brane probes of E-type Yukawa points lead to strongly coupled nearly conformal sectors nearby the Standard Model (visible sector) which are motivated by F-theory GUTs. Realistic visible sector brane configurations induce a seesaw mass hierarchy in the hidden sector with light GUT singlets charged under a strongly coupled hidden sector U(1). Interpreting these GUT singlets as dark matter, this leads to a matter genesis scenario where the freeze out and subsequent decay of heavy mediators between the two sectors simultaneously populates comparable amounts of baryon and dark matter asymmetry. Generating a net matter asymmetry requires a generational structure in the probe sector which is absent at weak string coupling, but is automatically realized at strong string coupling via towers of dyonic bound states corresponding to multi-prong string junctions. The hidden U(1) couples to the visible sector through both electric and magnetic kinetic mixing terms, providing an efficient means to deplete the symmetric component of dark matter. The mass of the dark matter is of order ~ 10 GeV. The dark matter mass and the matter asymmetry are both controlled by the scale of conformal symmetry breaking ~ 10^(9) - 10^(13) GeV, with the precise relation between the two set by details of the visible sector brane configuration.

Figures (7)

• Figure 1: Decay of a heavy $3-7_{vis}$ state connected between the probe D3-brane and the $7_{vis}$-brane. In order for Chan-Paton color flow to be conserved, this state decays into a Standard Model state $7_{vis}-7_{hid}$ string, and a $3-7_{hid}$ string which is a Standard Model singlet. The left column shows a depiction of the decay of a $3-7_{vis}$ string into one (top) and two (bottom) Standard Model states. In the right column the strong coupling analogue of these decays is indicated. At strong coupling there are additional spectator $3-7_{hid}$ states which dress the decay of the $3-7_{vis}$ string.
• Figure 2: Setup of F-theory GUTs. (a) In F-theory compactified to four dimensions with $\mathcal{N} = 1$ supersymmetry, the six internal directions and the profile of the axio-dilaton are combined into an elliptically fibered Calabi-Yau fourfold $X_4$ with threefold base $B_3$. (b) Various seven-branes are located at hypersurfaces where the torus degenerates. One stack gives the Standard Model gauge group, while the other stack corresponds to a flavor seven-brane. Intersections of matter seven-branes define Yukawa couplings and E-points. Also depicted is a D3-brane on the Coulomb branch of its moduli space.
• Figure 3: Decay of $\widetilde{Q}^{med}$ to $\widetilde{Q}^{hid}$ and $\ell_{(1)}$. The tree amplitude (left) is mediated from $\widetilde{Q}^{med}$ to $\widetilde{Q}^\dagger_{hid}$ by mass insertion for helicity flip and by Yukawa interaction $\lambda^\ell_{(1)}$. The one-loop amplitude (right) is mediated from $\widetilde{Q}^{med}$ to $\widetilde{Q}^\dagger_{hid}$ by virtual $\ell_{(i)}$ exchange and mass insertion for helicity flip. There are additional one-loop diagrams involving self-energy corrections which we have not drawn here. The Yukawa interactions $|\lambda^h_{(i)}|^2\lambda^\ell_{(1)}$ has the same phase as the tree amplitude. Consequently, there is no asymmetry between CP conjugate processes.
• Figure 4: The interaction of $(3-7_{vis})$ and $(3-7_{hid})$ states with the Standard Model particle $(7_{vis}-7_{hid})$. For a given $(7_{vis}-7_{hid})$ particle, there is an interaction with D3-brane states created by fundamental strings (diagram (a)) and also an interaction with states created by $(p,q)$ string junction (diagram (b)).
• Figure 5: Decay amplitude of $3-7_{vis}$ state at strong coupling. The decay amplitude consists of (a) diagonal interaction proportional to $\epsilon^{SM,SM}_I$, (b) transitional interaction proportional to $\epsilon^{SM,SM}_J$ times self-energy of initial state and (c) transitional interaction proportional to $\epsilon^{SM,SM}_I$ times self-energy of the final state.