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Numerical algorithms for problems in analysis and algebra, scientific computation

2 votes
1 answer
357 views

estimating lattice sums of concave functions

Suppose that $f$ is a twice-differentiable concave function from $R^2$ to $R$ that's negative outside of some bounded set (e.g. $f(x,y)=1-x^2-y^2$) and let $F=$max$(f,0)$. Let $S_n$ be the Riemann sum …
James Propp's user avatar
  • 19.7k
7 votes
3 answers
489 views

accelerating convergence of a class of sequences

Do any of the standard methods of acceleration convergence of series, when applied to the series $1 - 1 + 1/2 - 1/2 + 1/3 - 1/3 + ...$, give convergence to 0 with error $o(1/n)$? I tried applying Eul …
James Propp's user avatar
  • 19.7k
5 votes
2 answers
1k views

What is the definition of an antilimit?

I've seen some references to antilimits in the numerical analysis literature, but no definition of the term. The impression I get is that in specific contexts where every sequence $x_0,x_1,x_2,\dots$ …
James Propp's user avatar
  • 19.7k
8 votes
2 answers
2k views

error estimates for multi-dimensional Riemann sums

Suppose that $f$ is a continuous function of bounded variation from $R^2$ to $R$ that's negative outside of some bounded set, and let $F=\max(f,0)$. Let $S_n$ be the Riemann sum for the integral of $F …
James Propp's user avatar
  • 19.7k
3 votes
1 answer
435 views

Error of midpoint method for functions that are not twice-differentiable

All of the bounds I've seen for the error of the midpoint method of integration are expressed in terms of the second derivative of the function. What bounds are available when the function is not twi …
James Propp's user avatar
  • 19.7k
6 votes
3 answers
1k views

Dependence of error on mesh for Riemann sums

Suppose $f$ is continuous on $[a,b]$ with $I = \int_a^b f(x)\: dx$, and for every $\epsilon > 0$ let $\delta(\epsilon)$ be the largest $\delta > 0$ such that every Riemann sum arising from a partition …
James Propp's user avatar
  • 19.7k
5 votes
1 answer
540 views

Acceleration via smoothing

Is the following approach to accelerating the rate of convergence of $(1+1/2+\dots+1/n)- \ln n$ (with $n=1,2,3,\dots$), and other sequences like it, in the literature? Let $f(t)=(\sum_{1 \leq n \leq …
James Propp's user avatar
  • 19.7k
5 votes
0 answers
143 views

Error of midpoint method for differentiable functions

Is it the case that for every differentiable function $f$ on $[0,1]$ (with finite one-sided derivatives at the endpoints), the midpoint method of estimating $\int_0^1 f(x) \: dx$ has error $o(1/n)$? …
James Propp's user avatar
  • 19.7k
3 votes
2 answers
187 views

Seeking a class of functions for which sums approximate integrals well

Is there a "natural" class of integrable functions $f: {\mathbb R} \rightarrow {\mathbb R}$ for which it is true (and, preferably, not too hard to prove!) that $\sup_{0 \leq a < h} |h S(a,h) - I|$ is …
James Propp's user avatar
  • 19.7k