Simultaneously bounded and dense orbits for countably many diagonal flows

From papers

Let d3d\geq 3, let Xd=SLd(R)/SLd(Z)X_d=\mathrm{SL}_d(\mathbb{R})/\mathrm{SL}_d(\mathbb{Z}), and let Im,JnI_m,J_n be index sets. Choose nonzero vectors {v1,i}iIm{v2,j}jJn\{v^{1,i}\}_{i\in I_m}\cup\{v^{2,j}\}_{j\in J_n} in the diagonal subalgebra of sld(R)\mathfrak{sl}_d(\mathbb{R}) such that v1,iv2,jv^{1,i}\ne v^{2,j} for every (i,j)Im×Jn(i,j)\in I_m\times J_n. Define gt1,i=exp(tv1,i)g_t^{1,i}=\exp(tv^{1,i}) and gt2,j=exp(tv2,j)g_t^{2,j}=\exp(tv^{2,j}). Countable simultaneous-orbit conjecture. The set

iImB({gt1,i}t0)jJnD({gt2,j}t0)\bigcap_{i\in I_m}B(\{g_t^{1,i}\}_{t\geq 0})\cap\bigcap_{j\in J_n}D(\{g_t^{2,j}\}_{t\geq 0})

has full Hausdorff dimension in XdX_d. The cases with only bounded or only dense conditions are known in stronger forms, while the simultaneous general case is proposed as an open conjecture.

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Primary source

Dmitry Kleinbock and Chengyang Wu, “Simultaneously bounded and dense orbits for commuting Cartan actions”, arXiv:2509.05272 (2025).

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