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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 /vol1/1.2.10.lyx | |
| parent | 16ccda6c459c0fd7ca2081e9d541124c28b0c556 (diff) | |
Changed layout for more manageable volumes
Diffstat (limited to 'vol1/1.2.10.lyx')
| -rw-r--r-- | vol1/1.2.10.lyx | 1006 |
1 files changed, 1006 insertions, 0 deletions
diff --git a/vol1/1.2.10.lyx b/vol1/1.2.10.lyx new file mode 100644 index 0000000..a0a6bbd --- /dev/null +++ b/vol1/1.2.10.lyx @@ -0,0 +1,1006 @@ +#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 +exerc1[10] +\end_layout + +\end_inset + +Determine the value of +\begin_inset Formula $p_{n0}$ +\end_inset + + from Eqs. + (4) and (5) and interpret this result from the standpoint of Algorithm M. +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +answer +\end_layout + +\end_inset + +For +\begin_inset Formula $n=1$ +\end_inset + +, + +\begin_inset Formula $p_{10}=1$ +\end_inset + +, + and for +\begin_inset Formula $n>1$ +\end_inset + +, + +\begin_inset Formula +\[ +p_{n0}=\frac{1}{n}p_{(n-1)(-1)}+\frac{n-1}{n}p_{(n-1)0}=\frac{n-1}{n}p_{(n-1)0}=\dots=\frac{n-1}{n}\frac{n-2}{n-1}\cdots\frac{1}{2}p_{10}=\frac{1}{n}, +\] + +\end_inset + +so in general the probability that step M4 is never run (which happens when +\begin_inset Formula $a_{n}$ +\end_inset + + is already the maximum value) is +\begin_inset Formula $p_{n0}=\frac{1}{n}$ +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +exerc4[M10] +\end_layout + +\end_inset + +Give an explicit, + closed formula for the values of +\begin_inset Formula $p_{nk}$ +\end_inset + + in the coin-tossing experiment, + Eq. + (17). +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +answer +\end_layout + +\end_inset + + +\begin_inset Formula $p_{nk}=\binom{n}{k}p^{k}q^{n-k}$ +\end_inset + +. + To show that this derives from Eq. + (17), + we see that, + when +\begin_inset Formula $n=0$ +\end_inset + +, + +\begin_inset Formula $p_{0k}=\delta_{k0}$ +\end_inset + +, + matching the formula, + and then, + by induction, +\begin_inset Formula +\[ +p_{nk}=pp_{n-1,k-1}+qp_{n-1,k}=\binom{n-1}{k-1}p^{k}q^{n-k}+\binom{n-1}{k}p^{k}q^{n-k}=\binom{n}{k}p^{k}q^{n-k}. +\] + +\end_inset + + +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +rexerc8[M20] +\end_layout + +\end_inset + +Suppose that each +\begin_inset Formula $X[k]$ +\end_inset + + is taken at random from a set of +\begin_inset Formula $M$ +\end_inset + + distinct elements, + so that each of the +\begin_inset Formula $M^{n}$ +\end_inset + + possible choices for +\begin_inset Formula $X[1],X[2],\dots,X[n]$ +\end_inset + + is considered equally likely. + What is the probability that all the +\begin_inset Formula $X[k]$ +\end_inset + + will be distinct? +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +answer +\end_layout + +\end_inset + +We need calculate the number of choices out of those +\begin_inset Formula $M^{n}$ +\end_inset + + that do not repeat numbers. + These choices can be considered as taking a subset of +\begin_inset Formula $n$ +\end_inset + + elements from those +\begin_inset Formula $M$ +\end_inset + + (if +\begin_inset Formula $n>M$ +\end_inset + + then we must necessarily repeat) and then ordering them somehow, + so the total number of choices is +\begin_inset Formula $\binom{M}{n}n!$ +\end_inset + +, + and the probability is +\begin_inset Formula +\[ +\frac{\binom{M}{n}n!}{M^{n}}=\frac{M(M-1)\cdots(M-n+1)}{M^{n}}=\frac{M^{\underline{n}}}{M^{n}}. +\] + +\end_inset + + +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +rexerc11[M15] +\end_layout + +\end_inset + +What happens to the semi-invariants of a distribution if we change +\begin_inset Formula $G(z)$ +\end_inset + + to +\begin_inset Formula $F(z)=z^{n}G(z)$ +\end_inset + +? +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +answer +\end_layout + +\end_inset + +Let +\begin_inset Formula $H(z)\coloneqq z^{n}$ +\end_inset + +, + then +\begin_inset Formula $h(t)\coloneqq\ln H(\text{e}^{t})=\ln\text{e}^{nt}=nt$ +\end_inset + +, + so +\begin_inset Formula $\dot{h}(t)=n$ +\end_inset + + and +\begin_inset Formula $\ddot{h}(t)=\dddot{h}(t)=\dots=0$ +\end_inset + +. + Therefore +\begin_inset Formula +\begin{align*} +\kappa_{1} & =\dot{h}(0)=n; & \kappa_{n} & =h^{(n)}(0)=0, & n & >1. +\end{align*} + +\end_inset + +Thus, + by Theorem A, + the mean increases by +\begin_inset Formula $n$ +\end_inset + + and all the other semi-invariants stay the same. +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +rexerc20[M22] +\end_layout + +\end_inset + +Suppose we want to calculate +\begin_inset Formula $\max\{|a_{1}-b_{1}|,|a_{2}-b_{2}|,\dots,|a_{n}-b_{n}|\}$ +\end_inset + + when +\begin_inset Formula $b_{1}\leq b_{2}\leq\dots\leq b_{n}$ +\end_inset + +. + Show that it is sufficient to calculate +\begin_inset Formula $\max\{m_{\text{L}},m_{\text{R}}\}$ +\end_inset + +, + where +\begin_inset Formula +\begin{align*} +m_{\text{L}} & =\max\{a_{k}-b_{k}\mid a_{k}\text{ is a left-to-right maximum of }a_{1}a_{2}\cdots a_{n}\},\\ +m_{\text{R}} & =\max\{b_{k}-a_{k}\mid a_{k}\text{ is a right-to-left minimum of }a_{1}a_{2}\cdots a_{n}\}. +\end{align*} + +\end_inset + +(Thus, + if the +\begin_inset Formula $a$ +\end_inset + +'s are in random order, + the number of +\begin_inset Formula $k$ +\end_inset + +'s for which a subtraction must be performed is only about +\begin_inset Formula $2\ln n$ +\end_inset + +.) +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +answer +\end_layout + +\end_inset + +We interpret the concepts of +\begin_inset Quotes eld +\end_inset + +directional +\begin_inset Quotes erd +\end_inset + + maximum and minimum as meaning that +\begin_inset Formula $a_{k}\geq a_{k-1},\dots,a_{1}$ +\end_inset + + or that +\begin_inset Formula $a_{k}\leq a_{k+1},\dots,a_{n}$ +\end_inset + +, + respectively. + Then, + if +\begin_inset Formula $a_{j}$ +\end_inset + + is not a left-to-right maximum, + there is a +\begin_inset Formula $k<j$ +\end_inset + + with +\begin_inset Formula $a_{k}>a_{j}$ +\end_inset + + and therefore +\begin_inset Formula $a_{k}-b_{k}>a_{j}-b_{j}$ +\end_inset + + (as +\begin_inset Formula $b_{k}\leq b_{j}$ +\end_inset + +), + so +\begin_inset Formula $a_{j}-b_{j}$ +\end_inset + + is not a maximum of +\begin_inset Formula $\{a_{k}-b_{k}\}$ +\end_inset + +. + Similarly, + if +\begin_inset Formula $a_{j}$ +\end_inset + + is not a right-to-left minimum, + there is a +\begin_inset Formula $k>j$ +\end_inset + + with +\begin_inset Formula $a_{k}<a_{j}$ +\end_inset + + and +\begin_inset Formula $b_{k}-a_{k}>b_{j}-a_{j}$ +\end_inset + +. + +\end_layout + +\begin_layout Standard +Thus +\begin_inset Formula $m_{\text{L}}=\max\{a_{k}-b_{k}\}$ +\end_inset + + and +\begin_inset Formula $m_{\text{R}}=\max\{b_{k}-a_{k}\}$ +\end_inset + +. + Since at least one of them is non-negative, + +\begin_inset Formula $\max\{m_{\text{L}},m_{\text{R}}\}$ +\end_inset + + is also non-negative and it is therefore +\begin_inset Formula $|a_{k}-b_{k}|$ +\end_inset + + for some +\begin_inset Formula $k$ +\end_inset + +, + and it is no lower than any +\begin_inset Formula $|a_{j}-b_{j}|$ +\end_inset + + as those are either +\begin_inset Formula $a_{j}-b_{j}$ +\end_inset + + or +\begin_inset Formula $b_{j}-a_{j}$ +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +rexerc21[HM21] +\end_layout + +\end_inset + +Let +\begin_inset Formula $X$ +\end_inset + + be the number of heads that occur when a random coin is flipped +\begin_inset Formula $n$ +\end_inset + + times, + with generating function (18). + Use (25) to prove that +\begin_inset Formula +\[ +\text{Pr}(X\geq n(p+\epsilon))\leq\text{e}^{-\epsilon^{2}n/(2q)} +\] + +\end_inset + +when +\begin_inset Formula $\epsilon\geq0$ +\end_inset + +, + and obtain a similar estimate for +\begin_inset Formula $\text{Pr}(X\leq n(p-\epsilon))$ +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +answer +\end_layout + +\end_inset + +First, + we tackle the edge cases. + If +\begin_inset Formula $n=0$ +\end_inset + +, + then +\begin_inset Formula $X=0$ +\end_inset + + and +\begin_inset Formula $\text{Pr}(X\geq0)\leq1$ +\end_inset + + trivially, + so we may consider +\begin_inset Formula $n>0$ +\end_inset + +. + If +\begin_inset Formula $p=0$ +\end_inset + +, + then +\begin_inset Formula $\text{Pr}(X=0)=1$ +\end_inset + + and +\begin_inset Formula $\text{Pr}(X\geq n\epsilon)\leq\text{e}^{-\epsilon^{2}n/2}$ +\end_inset + + trivially, + so we may consider +\begin_inset Formula $p>0$ +\end_inset + +. + Finally, + if +\begin_inset Formula $\epsilon>q$ +\end_inset + + then +\begin_inset Formula $\text{Pr}(X\geq n(p+\epsilon))=0\leq\text{e}^{-\epsilon^{2}n/(2q)}$ +\end_inset + + and if +\begin_inset Formula $\epsilon=q$ +\end_inset + + then +\begin_inset Formula $\text{Pr}(X\geq n)=p^{n}\leq(\text{e}^{-q})^{n}\leq\text{e}^{-qn/2}$ +\end_inset + +, + using the fact that +\begin_inset Formula $t\leq\text{e}^{t-1}$ +\end_inset + + for every +\begin_inset Formula $t\in\mathbb{R}$ +\end_inset + +, + so we may consider +\begin_inset Formula $\epsilon<q$ +\end_inset + + and in particular +\begin_inset Formula $q>0$ +\end_inset + +. +\end_layout + +\begin_layout Standard +Now let +\begin_inset Formula $r=n(p+\epsilon)$ +\end_inset + +. + Then +\begin_inset Formula $\text{Pr}(X\geq n(p+\epsilon))\leq x^{-n(p+\epsilon)}(q+px)^{n}$ +\end_inset + +, + and we just need to find +\begin_inset Formula $x\geq1$ +\end_inset + + such that +\begin_inset Formula +\[ +\ln(q+px)-(p+\epsilon)\ln x\leq-\frac{\epsilon^{2}}{2q}. +\] + +\end_inset + + +\begin_inset Note Greyedout +status open + +\begin_layout Plain Layout +(I had to look at the solution, + esp. + for the right value of +\begin_inset Formula $x$ +\end_inset + +.) +\end_layout + +\end_inset + + If +\begin_inset Formula $x\coloneqq\frac{p+\epsilon}{p}\frac{q}{q-\epsilon}$ +\end_inset + +, + we have +\begin_inset Formula +\begin{multline*} +\ln(q+px)-(p+\epsilon)\ln x=\ln\left(q+(p+\epsilon)\frac{q}{q-\epsilon}\right)-(p+\epsilon)\ln\left(\frac{p+\epsilon}{p}\frac{q}{q-\epsilon}\right)=\\ +=\ln q-\ln(q-\epsilon)-(p+\epsilon)(\ln q-\ln(q-\epsilon)+\ln(p+\epsilon)-\ln p)=\\ +=(q-\epsilon)\ln\frac{q}{q-\epsilon}-(p+\epsilon)\ln\frac{p+\epsilon}{p}, +\end{multline*} + +\end_inset + +where we are assuming that +\begin_inset Formula $\epsilon<q$ +\end_inset + +. + Now, + by Eq. + 1.2.9(24), + let +\begin_inset Formula $v\coloneqq\frac{\epsilon}{q}$ +\end_inset + +, +\begin_inset Formula +\begin{multline*} +(q-\epsilon)\ln\frac{q}{q-\epsilon}=q(1-v)\ln\frac{1}{1-v}=q(v-1)\ln(1-v)=\\ +=q(v-1)\sum_{k\geq1}\frac{(-1)^{k+1}}{k}(-v)^{k}=q(1-v)\sum_{k\geq1}\frac{v^{k}}{k}=q\left(\sum_{k\geq1}\frac{v^{k}}{k}-\sum_{k\geq2}\frac{v^{k}}{k-1}\right)=\\ +=q\left(v-\sum_{k\geq2}\frac{v^{k}}{k(k-1)}\right)=\epsilon-\frac{\epsilon^{2}}{2q}-\frac{\epsilon^{3}}{6q^{2}}-\frac{\epsilon^{4}}{12q^{3}}-\dots\leq\epsilon-\frac{\epsilon^{2}}{2q}. +\end{multline*} + +\end_inset + +In addition, +\begin_inset Formula +\[ +-(p+\epsilon)\ln\frac{p+\epsilon}{p}=(p+\epsilon)\ln\frac{p}{p+\epsilon}=(p+\epsilon)\ln\left(1-\frac{\epsilon}{p+\epsilon}\right)\leq-\epsilon, +\] + +\end_inset + +so +\begin_inset Formula $-(p+\epsilon)\ln\frac{p+\epsilon}{p}\leq\epsilon$ +\end_inset + + and, + putting it all together, +\begin_inset Formula +\[ +\ln(q+px)-(p+\epsilon)\ln x\leq\cancel{\epsilon}-\frac{\epsilon^{2}}{2q}\cancel{-\epsilon}. +\] + +\end_inset + +For the second part, + switching the roles of heads and tails, + let +\begin_inset Formula $Y\coloneqq n-X$ +\end_inset + +, +\begin_inset Formula +\[ +\text{Pr}(X\leq n(p-\epsilon))=\text{Pr}(Y\geq n(q+\epsilon))\leq\text{e}^{-\epsilon^{2}n/(2p)}. +\] + +\end_inset + + +\end_layout + +\begin_layout Standard +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +rexerc22[HM22] +\end_layout + +\end_inset + +Suppose +\begin_inset Formula $X$ +\end_inset + + has the generating function +\begin_inset Formula $(q_{1}+p_{1}z)(q_{2}+p_{2}z)\cdots(q_{n}+p_{n}z)$ +\end_inset + +, + where +\begin_inset Formula $p_{k}+q_{k}=1$ +\end_inset + + for +\begin_inset Formula $1\leq k\leq n$ +\end_inset + +. + Let +\begin_inset Formula $\mu=EX=p_{1}+p_{2}+\dots+p_{n}$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +Prove that +\begin_inset Formula +\begin{align*} +\text{Pr}(X\leq\mu r) & \leq(r^{-r}\text{e}^{r-1})^{\mu}, & \text{when }0 & <r\leq1;\\ +\text{Pr}(X\geq\mu r) & \leq(r^{-r}\text{e}^{r-1})^{\mu}, & \text{when }r & \geq1. +\end{align*} + +\end_inset + + +\end_layout + +\begin_layout Enumerate +Express the right-hand sides of these estimates in convenient form when +\begin_inset Formula $r\approx1$ +\end_inset + +. +\end_layout + +\begin_layout Enumerate +Show that if +\begin_inset Formula $r$ +\end_inset + + is sufficiently large we have +\begin_inset Formula $\text{Pr}(X\geq\mu r)\leq2^{-\mu r}$ +\end_inset + +. +\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 +For the first equation, + using Eq. + (24) with +\begin_inset Formula $x=r$ +\end_inset + +, +\begin_inset Formula +\begin{multline*} +\text{Pr}(X\leq\mu r)\leq r^{-\mu r}(q_{1}+p_{1}r)\cdots(q_{n}+p_{n}r)=r^{-\mu r}\prod_{k}(q_{k}+p_{k}r)=\\ +=r^{-\mu r}\prod_{k}(1+p_{k}(r-1))\leq r^{-\mu r}\prod_{k}\text{e}^{p_{k}(r-1)}=r^{-\mu r}\text{e}^{\mu(r-1)}=(r^{-r}\text{e}^{r-1})^{\mu}. +\end{multline*} + +\end_inset + +For the second equation, + repeat the same steps but using Eq. + (25). +\end_layout + +\begin_layout Enumerate +When +\begin_inset Formula $r\approx1$ +\end_inset + +, + +\begin_inset Formula $r\approx\text{e}^{r-1}$ +\end_inset + +, + so +\begin_inset Formula $(r^{-r}\text{e}^{r-1})^{\mu}\approx r^{\mu(1-r)}$ +\end_inset + +. + The inequality still holds for +\begin_inset Formula $r<2$ +\end_inset + + since, + in the previous proof, + we can see that +\begin_inset Formula $1+p_{k}(r-1)\leq r^{p_{k}}$ +\end_inset + + by taking the Taylor series of the logarithms: +\begin_inset Formula +\begin{multline*} +\ln(1+p_{k}(r-1))=p_{k}(r-1)-\frac{p_{k}^{2}(r-1)^{2}}{2}+\frac{p_{k}^{3}(r-1)^{3}}{3}-\frac{p_{k}^{4}(r-1)^{4}}{4}+\dots\leq\\ +\leq p_{k}(r-1)-\frac{p_{k}(r-1)^{2}}{2}+\frac{p_{k}(r-1)^{3}}{3}-\frac{p_{k}(r-1)^{4}}{4}+\dots=p_{k}\ln r. +\end{multline*} + +\end_inset + +Using this inequality instead of the one we used gives the proper result. +\end_layout + +\begin_layout Enumerate +Clearly +\begin_inset Formula $1+p_{k}(r-1)\leq r$ +\end_inset + +, + so +\begin_inset Formula $r^{-\mu r}\prod_{k}(1+p_{k}(r-1))\leq r^{-\mu r}r^{n}$ +\end_inset + +, + and we want to see that this in turn is less than +\begin_inset Formula $2^{-\mu r}$ +\end_inset + + for large enough +\begin_inset Formula $r$ +\end_inset + +. + Now, +\begin_inset Formula +\[ +\frac{r^{n}r^{-\mu r}}{2^{-\mu r}}=r^{n}\left(\frac{2}{r}\right)^{\mu r}, +\] + +\end_inset + +and since +\begin_inset Formula $\left(\frac{2}{r}\right)^{\mu r}$ +\end_inset + + decreases faster than +\begin_inset Formula $r^{n}$ +\end_inset + + increases, + there exist +\begin_inset Formula $r_{0}$ +\end_inset + + such that, + for +\begin_inset Formula $r>r_{0}$ +\end_inset + +, + this fraction is less than 1. +\end_layout + +\end_body +\end_document |
