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| author | Juan Marín Noguera <juan@mnpi.eu> | 2025-05-16 22:18:44 +0200 |
|---|---|---|
| committer | Juan Marín Noguera <juan@mnpi.eu> | 2025-05-16 22:18:44 +0200 |
| commit | 4f670b750af5c11e1eac16d9cd8556455f89f46a (patch) | |
| tree | e0f8d7b33df2727d89150f799ee8628821fda80a /1.2.11.2.lyx | |
| parent | 16ccda6c459c0fd7ca2081e9d541124c28b0c556 (diff) | |
Changed layout for more manageable volumes
Diffstat (limited to '1.2.11.2.lyx')
| -rw-r--r-- | 1.2.11.2.lyx | 440 |
1 files changed, 0 insertions, 440 deletions
diff --git a/1.2.11.2.lyx b/1.2.11.2.lyx deleted file mode 100644 index cd12585..0000000 --- a/1.2.11.2.lyx +++ /dev/null @@ -1,440 +0,0 @@ -#LyX 2.4 created this file. For more info see https://www.lyx.org/ -\lyxformat 620 -\begin_document -\begin_header -\save_transient_properties true -\origin unavailable -\textclass book -\use_default_options true -\maintain_unincluded_children no -\language american -\language_package default -\inputencoding utf8 -\fontencoding auto -\font_roman "default" "default" -\font_sans "default" "default" -\font_typewriter "default" "default" -\font_math "auto" "auto" -\font_default_family default -\use_non_tex_fonts false -\font_sc false -\font_roman_osf false -\font_sans_osf false -\font_typewriter_osf false -\font_sf_scale 100 100 -\font_tt_scale 100 100 -\use_microtype false -\use_dash_ligatures true -\graphics default -\default_output_format default -\output_sync 0 -\bibtex_command default -\index_command default -\float_placement class -\float_alignment class -\paperfontsize default -\spacing single -\use_hyperref false -\papersize default -\use_geometry false -\use_package amsmath 1 -\use_package amssymb 1 -\use_package cancel 1 -\use_package esint 1 -\use_package mathdots 1 -\use_package mathtools 1 -\use_package mhchem 1 -\use_package stackrel 1 -\use_package stmaryrd 1 -\use_package undertilde 1 -\cite_engine basic -\cite_engine_type default -\biblio_style plain -\use_bibtopic false -\use_indices false -\paperorientation portrait -\suppress_date false -\justification true -\use_refstyle 1 -\use_formatted_ref 0 -\use_minted 0 -\use_lineno 0 -\index Index -\shortcut idx -\color #008000 -\end_index -\secnumdepth 3 -\tocdepth 3 -\paragraph_separation indent -\paragraph_indentation default -\is_math_indent 0 -\math_numbering_side default -\quotes_style english -\dynamic_quotes 0 -\papercolumns 1 -\papersides 1 -\paperpagestyle default -\tablestyle default -\tracking_changes false -\output_changes false -\change_bars false -\postpone_fragile_content true -\html_math_output 0 -\html_css_as_file 0 -\html_be_strict false -\docbook_table_output 0 -\docbook_mathml_prefix 1 -\end_header - -\begin_body - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc4[HM20] -\end_layout - -\end_inset - -( -\emph on -Sums of powers. -\emph default -) When -\begin_inset Formula $f(x)=x^{m}$ -\end_inset - -, - the high-order derivatives of -\begin_inset Formula $f$ -\end_inset - - are all zero, - so Euler's summation formula gives an -\emph on -exact -\emph default - value for the sum -\begin_inset Formula -\[ -S_{m}(n)=\sum_{0\leq k<n}k^{m} -\] - -\end_inset - -in terms of Bernoulli numbers. - (It was the study of -\begin_inset Formula $S_{m}(n)$ -\end_inset - - for -\begin_inset Formula $m=1,2,3,\dots$ -\end_inset - - that led Bernoulli and Seki to discover those numbers in the first place.) Express -\begin_inset Formula $S_{m}(n)$ -\end_inset - - in terms of Bernoulli -\emph on -polynomials -\emph default -. - Check your answer for -\begin_inset Formula $m=0$ -\end_inset - -, - 1, - and 2. - (Note that the desired sum is performed for -\begin_inset Formula $0\leq k<n$ -\end_inset - - instead of -\begin_inset Formula $1\leq k<n$ -\end_inset - -; - Euler's summation formula may be applied with 0 replacing 1 throughout.) -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -For -\begin_inset Formula $k\geq0$ -\end_inset - -, - we have -\begin_inset Formula $f^{(k)}(x)=m^{\underline{k}}x^{m-k}$ -\end_inset - -. - If -\begin_inset Formula $k<m$ -\end_inset - -, - this is nonzero except that -\begin_inset Formula $f^{(k)}(0)=0$ -\end_inset - -; - if -\begin_inset Formula $k=m$ -\end_inset - -, - -\begin_inset Formula $f^{(m)}(x)\equiv1$ -\end_inset - -, - and if -\begin_inset Formula $k>m$ -\end_inset - -, - -\begin_inset Formula $f^{(k)}(x)\equiv0$ -\end_inset - -. - Using Euler's summation formula, - when -\begin_inset Formula $m\geq1$ -\end_inset - -, -\begin_inset Formula -\[ -S_{m}(n)=\sum_{0\leq k<n}k^{m}=\int_{0}^{n}x^{m}\text{d}x+\sum_{k=1}^{m}\frac{B_{k}}{k!}m^{\underline{k-1}}n^{m-k+1}=\frac{n^{m+1}}{m+1}+\sum_{k=1}^{m}\frac{B_{k}}{m-k+1}\binom{m}{k}n^{m-k+1}. -\] - -\end_inset - -Then, -\begin_inset Formula -\[ -S'_{m}(n)=n^{m}+\sum_{k=1}^{m}B_{k}\binom{m}{k}n^{m-k}=\sum_{k}B_{k}\binom{m}{k}n^{m-k}=B_{m}(x), -\] - -\end_inset - -which means that -\begin_inset Formula -\[ -\int_{0}^{n}B_{m}=(S_{m}(n)-S_{m}(0))=S_{m}(n) -\] - -\end_inset - - and therefore, -\begin_inset Formula -\[ -S_{m}(n)=\int_{0}^{n}B_{m}. -\] - -\end_inset - -Now we check the solution, - and in particular we check that this works for -\begin_inset Formula $m=0$ -\end_inset - - as well: -\begin_inset Formula -\begin{align*} -\int_{0}^{n}B_{0} & =\int_{0}^{n}\text{d}x=n-0=n, & S_{0}(n) & =\sum_{0\leq k<n}1=n;\\ -\int_{0}^{n}B_{1} & =\int_{0}^{n}(x-\tfrac{1}{2})\text{d}x=\frac{n^{2}-n}{2}, & S_{1}(n) & =\sum_{0\leq k<n}k=\frac{n(n-1)}{2};\\ -\int_{0}^{n}B_{2} & =\int_{0}^{n}(x^{2}-x+\tfrac{1}{6})\text{d}x=\frac{2n^{3}-3n^{2}+n}{6}, -\end{align*} - -\end_inset - -and we check the last result we use induction. - For -\begin_inset Formula $n=0$ -\end_inset - -, - -\begin_inset Formula $S_{2}(0)=0$ -\end_inset - -. - For -\begin_inset Formula $n\geq0$ -\end_inset - -, -\begin_inset Formula -\begin{align*} -S_{2}(n) & =\frac{1}{6}\left(2(n-1)^{3}-3(n-1)^{2}+(n-1)\right)+(n-1)^{2}\\ - & =\frac{1}{6}\left(2n^{3}\cancel{-6n^{2}}\cancel{+6n}\cancel{-2}-3n^{2}\cancel{+6n}\cancel{-3}+n\cancel{-1}\cancel{+6n^{2}}\cancel{-12n}\cancel{+6}\right)=\int_{0}^{n}B_{2}. -\end{align*} - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc9[M25] -\end_layout - -\end_inset - -Find the asymptotic value of -\begin_inset Formula $\binom{2n}{n}$ -\end_inset - - with a relative error of -\begin_inset Formula $O(n^{-3})$ -\end_inset - -, - in two ways: -\end_layout - -\begin_layout Enumerate -via Stirling's approximation; -\end_layout - -\begin_layout Enumerate -via exercise 1.2.6–47 and Eq. - 1.2.11.1–(16). -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Enumerate -We have, -\begin_inset Formula -\[ -\binom{2n}{n}=\frac{(2n)!}{n!^{2}}, -\] - -\end_inset - -so -\begin_inset Formula -\begin{multline*} -\ln\binom{2n}{n}=\ln(2n)!-2\ln(n!)=\\ -=(2n+\tfrac{1}{2})\ln(2n)-2n+\sigma+\frac{1}{24n}-(2n+1)\ln n+2n-2\sigma-\frac{1}{6n}+O(n^{-3})=\\ -=(2n+\tfrac{1}{2})(\ln n+\ln2)-(2n+1)\ln n-\sigma-\frac{1}{8n}+O(n^{-3})=\\ -=(2n+\tfrac{1}{2})\ln2-\frac{\ln n}{2}-\sigma-\frac{1}{8n}+O(n^{-3}), -\end{multline*} - -\end_inset - -and therefore -\begin_inset Formula -\[ -\binom{2n}{n}=\exp(\cdots)=\frac{2^{2n}}{\sqrt{\pi n}}\left(1-\frac{1}{8n}+\frac{1}{128n^{2}}+O(n^{3})\right). -\] - -\end_inset - - -\end_layout - -\begin_layout Enumerate -\begin_inset Note Greyedout -status open - -\begin_layout Plain Layout -(I had to look up the solution.) -\end_layout - -\end_inset - -Exercise 1.2.6–47, - when -\begin_inset Formula $r=-1/2$ -\end_inset - -, - the first identity simplifies to -\begin_inset Formula -\[ -(-1)^{k}\binom{-\frac{1}{2}}{k}=(-1)^{k}\binom{-k-1}{k}\Bigg/4^{k}=\binom{2k}{k}\Bigg/4^{k}. -\] - -\end_inset - -Thus, - using Eq. - 1.2.6–(21), -\begin_inset Formula -\begin{multline*} -\binom{2n}{n}=4^{n}(-1)^{n}\binom{-\frac{1}{2}}{n}=4^{n}\binom{n-\frac{1}{2}}{n}=4^{n}\frac{\Gamma(n+\frac{1}{2})}{\Gamma(n+1)\Gamma(\frac{1}{2})}=4^{k}\frac{\Gamma(n+\frac{1}{2})}{n\Gamma(n)\sqrt{\pi}}=\\ -=\frac{4^{n}n^{\overline{1/2}}}{n\sqrt{\pi}}=\frac{2^{2n}}{n\sqrt{\pi}}\left(\stirla{1/2}{1/2}n^{1/2}+\stirla{1/2}{-1/2}n^{-1/2}+\stirla{1/2}{-3/2}n^{-3/2}+O(n^{-5/2})\right). -\end{multline*} - -\end_inset - -Using Eqs. - 1.2.6–(48), - (49), - and (57), -\begin_inset Formula -\begin{align*} -\stirla{1/2}{1/2} & =1,\\ -\stirla{1/2}{-1/2} & =\binom{1/2}{2}=\frac{\frac{1}{2}(-\frac{1}{2})}{2}=-\frac{1}{8},\\ -\stirla{1/2}{-3/2} & =\binom{1/2}{4}+2\binom{3/2}{4}=\frac{-\frac{15}{16}}{24}+2\frac{\frac{9}{16}}{24}=\frac{3}{16\cdot24}=\frac{1}{128}, -\end{align*} - -\end_inset - -so in the end, -\begin_inset Formula -\[ -\binom{2n}{n}=\frac{2^{2n}}{\sqrt{\pi n}}\left(1-\frac{1}{8n}+\frac{1}{128n^{2}}+O(n^{-3})\right). -\] - -\end_inset - - -\end_layout - -\end_body -\end_document |
