332,273 research outputs found
On The Hereditary Discrepancy of Homogeneous Arithmetic Progressions
We show that the hereditary discrepancy of homogeneous arithmetic
progressions is lower bounded by . This bound is tight up
to the constant in the exponent. Our lower bound goes via proving an
exponential lower bound on the discrepancy of set systems of subcubes of the
boolean cube .Comment: To appear in the Proceedings of the American Mathematical Societ
On the inducibility of cycles
In 1975 Pippenger and Golumbic proved that any graph on vertices admits
at most induced -cycles. This bound is larger by a
multiplicative factor of than the simple lower bound obtained by a blow-up
construction. Pippenger and Golumbic conjectured that the latter lower bound is
essentially tight. In the present paper we establish a better upper bound of
. This constitutes the first progress towards proving
the aforementioned conjecture since it was posed
Bounds on the permanent and some applications
We give new lower and upper bounds on the permanent of a doubly stochastic
matrix. Combined with previous work, this improves on the deterministic
approximation factor for the permanent.
We also give a combinatorial application of the lower bound, proving S.
Friedland's "Asymptotic Lower Matching Conjecture" for the monomer-dimer
problem
The Minrank of Random Graphs
The minrank of a graph is the minimum rank of a matrix that can be
obtained from the adjacency matrix of by switching some ones to zeros
(i.e., deleting edges) and then setting all diagonal entries to one. This
quantity is closely related to the fundamental information-theoretic problems
of (linear) index coding (Bar-Yossef et al., FOCS'06), network coding and
distributed storage, and to Valiant's approach for proving superlinear circuit
lower bounds (Valiant, Boolean Function Complexity '92).
We prove tight bounds on the minrank of random Erd\H{o}s-R\'enyi graphs
for all regimes of . In particular, for any constant ,
we show that with high probability,
where is chosen from . This bound gives a near quadratic
improvement over the previous best lower bound of (Haviv and
Langberg, ISIT'12), and partially settles an open problem raised by Lubetzky
and Stav (FOCS '07). Our lower bound matches the well-known upper bound
obtained by the "clique covering" solution, and settles the linear index coding
problem for random graphs.
Finally, our result suggests a new avenue of attack, via derandomization, on
Valiant's approach for proving superlinear lower bounds for logarithmic-depth
semilinear circuits
Super-Logarithmic Lower Bounds for Dynamic Graph Problems
In this work, we prove a unconditional lower
bound on the maximum of the query time and update time for dynamic data
structures supporting reachability queries in -node directed acyclic graphs
under edge insertions. This is the first super-logarithmic lower bound for any
natural graph problem. In proving the lower bound, we also make novel
contributions to the state-of-the-art data structure lower bound techniques
that we hope may lead to further progress in proving lower bounds
Lower bound for the quantum capacity of a discrete memoryless quantum channel
We generalize the random coding argument of stabilizer codes and derive a
lower bound on the quantum capacity of an arbitrary discrete memoryless quantum
channel. For the depolarizing channel, our lower bound coincides with that
obtained by Bennett et al. We also slightly improve the quantum
Gilbert-Varshamov bound for general stabilizer codes, and establish an analogue
of the quantum Gilbert-Varshamov bound for linear stabilizer codes. Our proof
is restricted to the binary quantum channels, but its extension of to l-adic
channels is straightforward.Comment: 16 pages, REVTeX4. To appear in J. Math. Phys. A critical error in
fidelity calculation was corrected by using Hamada's result
(quant-ph/0112103). In the third version, we simplified formula and
derivation of the lower bound by proving p(Gamma)+q(Gamma)=1. In the second
version, we added an analogue of the quantum Gilbert-Varshamov bound for
linear stabilizer code
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