16,942,917 research outputs found
Quantified Derandomization of Linear Threshold Circuits
One of the prominent current challenges in complexity theory is the attempt
to prove lower bounds for , the class of constant-depth, polynomial-size
circuits with majority gates. Relying on the results of Williams (2013), an
appealing approach to prove such lower bounds is to construct a non-trivial
derandomization algorithm for . In this work we take a first step towards
the latter goal, by proving the first positive results regarding the
derandomization of circuits of depth .
Our first main result is a quantified derandomization algorithm for
circuits with a super-linear number of wires. Specifically, we construct an
algorithm that gets as input a circuit over input bits with
depth and wires, runs in almost-polynomial-time, and
distinguishes between the case that rejects at most inputs
and the case that accepts at most inputs. In fact, our
algorithm works even when the circuit is a linear threshold circuit, rather
than just a circuit (i.e., is a circuit with linear threshold gates,
which are stronger than majority gates).
Our second main result is that even a modest improvement of our quantified
derandomization algorithm would yield a non-trivial algorithm for standard
derandomization of all of , and would consequently imply that
. Specifically, if there exists a quantified
derandomization algorithm that gets as input a circuit with depth
and wires (rather than wires), runs in time at
most , and distinguishes between the case that rejects at
most inputs and the case that accepts at most
inputs, then there exists an algorithm with running time
for standard derandomization of .Comment: Changes in this revision: An additional result (a PRG for quantified
derandomization of depth-2 LTF circuits); rewrite of some of the exposition;
minor correction
Axiomatizing Petri Net Concatenable Processes
The concatenable processes of a Petri net can be characterized abstractly as the arrows of a symmetric monoidal category . Yet, this is only a partial axiomatization, since is built on a concrete, ad hoc chosen, category of symmetries. In this paper we give a fully equational description of the category of concatenable processes of , thus yielding an axiomatic theory of the noninterleaving behaviour of Petri nets
On the structure of P(n)*P(n) for p=2
We show that P(n)*(P(n)) for p = 2 with its geometrically induced structure maps is not an Hopf algebroid because neither the augmentation Epsilon nor the coproduct Delta are multiplicative. As a consequence the algebra structure of P(n)*(P(n)) is slightly different from what was supposed to be the case. We give formulas for Epsilon(xy) and Delta(xy) and show that the inversion of the formal group of P(n) is induced by an antimultiplicative involution Xi : P(n) -> P(n). Some consequences for multiplicative and antimultiplicative automorphisms of K(n) for p = 2 are also discussed
Measurement of the ratio Gamma(K_L -> gamma gamma)/Gamma(K_L -> pi^0 pi^0 pi^0) with the KLOE detector
We have measured the ratio R=Gamma(K_L -> gamma gamma)/ \Gamma(K_L -> 3 pi^0)
using the KLOE detector. From a sample of ~ 10^9 phi-mesons produced at DAFNE,
the Frascati phi-factory, we select ~ 1.6 10^8 K_L-mesons tagged by observing
K_S -> pi^+ pi^- following the reaction e^+ e^- -> phi -> K_L K_S. From this
sample we select 27,375 K_L -> gamma gamma events and obtain R = (2.79 \pm
0.02_{stat} \pm 0.02_{syst}) \times 10^{-3}. Using the world average value for
BR(K_{L} -> 3 pi^0), we obtain BR(K_{L} -> gamma gamma) = (5.89 \pm 0.07 \pm
0.08) \times 10^{-4} where the second error is due to the uncertainty on the 3
pi^0 branching fraction.Comment: 14 page
Projectile Excitations in Reactions
It has recently been proven from measurements of the spin-transfer
coefficients and that there is a small but non-vanishing
component , in the inclusive reaction
cross section . It is shown that the dominant part of the measured
can be explained in terms of the projectile excitation
mechanism. An estimate is further made of contributions to from
s-wave rescattering process. It is found that s-wave rescattering contribution
is much smaller than the contribution coming from projectile
excitation mechanism. The addition of s-wave rescattering contribution to the
dominant part, however, improves the fit to the data.Comment: 9 pages, Revtex, figures can be obtained upon reques
N,N'-(p-Phenylene)dibenzamide (PPDB)
C20N202H16, monoclinic, P2~/c, a = 18.065(1), b = 5.247(1), c = 8.027(1) A, fl = 93.99 (1) °, Z = 2. The crystal structure has been refined by least-squares techniques. R w = 7.3%. The structure contains planar phenyl rings which are\ud
rotated with respect to the plane of the amide group owing to steric hindrance. The molecules are connected in one dimension by means of hydrogen bonds
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