Nisheeth K. Vishnoi

  1. $2^{\log^{1-\eps} n}$ Hardness for Closest Vector Problem with Preprocessing.

    Authors: Nisheeth K. Vishnoi, Subhash Khot, Preyas Popat
    Subjects: Computational Complexity
    Abstract

    We prove that for an arbitrarily small constant $\eps>0,$ assuming NP$\not
    \subseteq$DTIME$(2^{{\log^{O(1/\eps)} n}})$, the preprocessing versions of the
    closest vector problem and the nearest codeword problem are hard to approximate
    within a factor better than $2^{\log ^{1-\eps}n}.$ This improves upon the
    previous hardness factor of $(\log n)^\delta$ for some $\delta > 0$ due to
    \cite{AKKV05}.

  2. Algorithms and Hardness for Subspace Approximation.

    Authors: Amit Deshpande, Kasturi Varadarajan, Madhur Tulsiani, Nisheeth K. Vishnoi
    Subjects: Data Structures and Algorithms
    Abstract

    The subspace approximation problem Subspace($k$,$p$) asks for a
    $k$-dimensional linear subspace that fits a given set of points optimally,
    where the error for fitting is a generalization of the least squares fit and
    uses the $\ell_{p}$ norm instead. Most of the previous work on subspace
    approximation has focused on small or constant $k$ and $p$, using coresets and
    sampling techniques from computational geometry.

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