Complexity of Lattice Problems
Complexity of Lattice Problems
The inapproximability of lattice and coding problems with preprocessing
Journal of Computer and System Sciences - Special issue on computational complexity 2002
Journal of the ACM (JACM)
Nonembeddability theorems via Fourier analysis
FOCS '05 Proceedings of the 46th Annual IEEE Symposium on Foundations of Computer Science
Worst-Case to Average-Case Reductions Based on Gaussian Measures
SIAM Journal on Computing
Proceedings of the forty-second ACM symposium on Theory of computing
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We show that for every n-dimensional lattice L the torus Rn/L can be embedded with distortion O(nċ√logn) into a Hilbert space. This improves the exponential upper bound of O(n3n/2) due to Khot and Naor (FOCS 2005, Math. Annal. 2006) and gets close to their lower bound of Ω(√n). We also obtain tight bounds for certain families of lattices. Our main new ingredient is an embedding that maps any point u ∈ Rn/L to a Gaussian function centered at u in the Hilbert space L2(Rn/L). The proofs involve Gaussian measures on lattices, the smoothing parameter of lattices and Korkine-Zolotarev bases.