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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 /3.2.1.2.lyx | |
| parent | 16ccda6c459c0fd7ca2081e9d541124c28b0c556 (diff) | |
Changed layout for more manageable volumes
Diffstat (limited to '3.2.1.2.lyx')
| -rw-r--r-- | 3.2.1.2.lyx | 1542 |
1 files changed, 0 insertions, 1542 deletions
diff --git a/3.2.1.2.lyx b/3.2.1.2.lyx deleted file mode 100644 index ad58b78..0000000 --- a/3.2.1.2.lyx +++ /dev/null @@ -1,1542 +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 -\begin_preamble -\input defs -\end_preamble -\use_default_options true -\maintain_unincluded_children no -\language english -\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 false -\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 - -What is the length of the period of the linear congruential sequence with -\begin_inset Formula $X_{0}=5772156648$ -\end_inset - -, - -\begin_inset Formula $a=3141592621$ -\end_inset - -, - -\begin_inset Formula $c=2718281829$ -\end_inset - -, - and -\begin_inset Formula $m=10000000000$ -\end_inset - -? -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -Obviously -\begin_inset Formula $c$ -\end_inset - - is relatively prime to -\begin_inset Formula $m$ -\end_inset - -. - Furthermore, - the prime divisors of -\begin_inset Formula $m$ -\end_inset - - are 2 and 5 and -\begin_inset Formula $a-1$ -\end_inset - - is a multiple of both 4 and 5. - Therefore the length is -\begin_inset Formula $m$ -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -exerc2[10] -\end_layout - -\end_inset - -Are the following two conditions sufficient to guarantee the maximum length period, - when -\begin_inset Formula $m$ -\end_inset - - is a power of 2? -\end_layout - -\begin_layout Enumerate -\begin_inset Formula $c$ -\end_inset - - is odd; -\end_layout - -\begin_layout Enumerate -\begin_inset Formula $a\bmod4=1$ -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -Yes, - by theorem A. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc6[20] -\end_layout - -\end_inset - -Find all multipliers -\begin_inset Formula $a$ -\end_inset - - that satisfy the conditions of Theorem A when -\begin_inset Formula $m=10^{6}-1$ -\end_inset - -. - (See Table 3.2.1.1–1.) -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -By the table, - -\begin_inset Formula $m=3^{3}\cdot7\cdot11\cdot13\cdot37$ -\end_inset - -. - Multipliers are numbers -\begin_inset Formula $a$ -\end_inset - - such that -\begin_inset Formula -\[ -a\bmod3=a\bmod7=a\bmod11=a\bmod13=a\bmod37=1. -\] - -\end_inset - -These identities tell us that -\begin_inset Formula $a\equiv1\pmod{3\cdot7\cdot11\cdot13\cdot37=m/3^{2}=111111}$ -\end_inset - -, - so the possible values are -\begin_inset Formula $1,111112,222223,333334,444445,555556,666667,777778,888889$ -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc7[M23] -\end_layout - -\end_inset - -The period of a congruential sequence need not start with -\begin_inset Formula $X_{0}$ -\end_inset - -, - but we can always find indices -\begin_inset Formula $\mu\geq0$ -\end_inset - - and -\begin_inset Formula $\lambda>0$ -\end_inset - - such that -\begin_inset Formula $X_{n+\lambda}=X_{n}$ -\end_inset - - whenever -\begin_inset Formula $n\geq\mu$ -\end_inset - -, - and for which -\begin_inset Formula $\mu$ -\end_inset - - and -\begin_inset Formula $\lambda$ -\end_inset - - are the smallest possible values with this property. - (See exercises 3.1–6 and 3.2.1–1.) If -\begin_inset Formula $\mu_{j}$ -\end_inset - - and -\begin_inset Formula $\lambda_{j}$ -\end_inset - - are the indices corresponding to the sequences -\begin_inset Formula -\[ -(X_{0}\bmod p_{j}^{e_{j}},a\bmod p_{j}^{e_{j}},c\bmod p_{j}^{e_{j}},p_{j}^{e_{j}}), -\] - -\end_inset - -and if -\begin_inset Formula $\mu$ -\end_inset - - and -\begin_inset Formula $\lambda$ -\end_inset - - correspond to the composite sequence -\begin_inset Formula $(X_{0},a,c,p_{1}^{e_{1}}\cdots p_{t}^{e_{t}})$ -\end_inset - -, - Lemma Q states that -\begin_inset Formula $\lambda$ -\end_inset - - is the least common multiple of -\begin_inset Formula $\lambda_{1},\dots,\lambda_{t}$ -\end_inset - -. - What is the value of -\begin_inset Formula $\mu$ -\end_inset - - in terms of the values of -\begin_inset Formula $\mu_{1},\dots,\mu_{t}$ -\end_inset - -? - What is the maximum possible value of -\begin_inset Formula $\mu$ -\end_inset - - obtainable by varying -\begin_inset Formula $X_{0}$ -\end_inset - -, - -\begin_inset Formula $a$ -\end_inset - -, - and -\begin_inset Formula $c$ -\end_inset - -, - when -\begin_inset Formula $m=p_{1}^{e_{1}}\cdots p_{t}^{e_{t}}$ -\end_inset - - is fixed? -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -Since the -\begin_inset Formula $j$ -\end_inset - -th sequence has values -\begin_inset Formula $X_{n}\bmod p_{j}^{e_{j}}$ -\end_inset - -, - and the -\begin_inset Formula $X_{n}$ -\end_inset - - are uniquely determined by such values for all -\begin_inset Formula $j$ -\end_inset - -, - -\begin_inset Formula $(X_{n})_{n}$ -\end_inset - - enters into a loop whenever all the -\begin_inset Formula $X_{n}\bmod p_{j}^{e_{j}}$ -\end_inset - - have entered into a loop, - that is, - -\begin_inset Formula $\mu=\max_{j}\mu_{j}$ -\end_inset - -. - We are left to see what is the maximum -\begin_inset Formula $\mu$ -\end_inset - - when -\begin_inset Formula $m=p^{e}$ -\end_inset - - for some prime number -\begin_inset Formula $p$ -\end_inset - - and positive integer -\begin_inset Formula $e$ -\end_inset - - (for -\begin_inset Formula $m=1$ -\end_inset - -, - -\begin_inset Formula $\mu=0$ -\end_inset - -). - In this case, - -\begin_inset Formula $\mu$ -\end_inset - - is the lowest number such that -\begin_inset Formula -\[ -X_{\mu}=X_{\mu+\lambda}\equiv X_{\mu}a^{\lambda}+\frac{a^{\lambda}-1}{a-1}c\pmod{p^{e}}, -\] - -\end_inset - -if and only if -\begin_inset Formula $X_{\mu}(1-a^{\lambda})\equiv\frac{a^{\lambda}-1}{a-1}c\pmod{p^{e}}$ -\end_inset - -, - so for -\begin_inset Formula $\mu>0$ -\end_inset - -, - -\begin_inset Formula $\mu-1$ -\end_inset - - must be a number such that -\begin_inset Formula -\begin{align*} -X_{\mu-1}(1-a^{\lambda}) & \not\equiv\frac{a^{\lambda}-1}{a-1}c, & aX_{\mu-1}(1-a^{\lambda}) & \equiv a\frac{a^{\lambda}-1}{a-1}c & & \pmod{p^{e}}, -\end{align*} - -\end_inset - -where the first equation comes from changing -\begin_inset Formula $\mu$ -\end_inset - - to -\begin_inset Formula $\mu-1$ -\end_inset - - above and the second one from changing -\begin_inset Formula $X_{\mu}$ -\end_inset - - to -\begin_inset Formula $aX_{\mu-1}+c$ -\end_inset - - and rearranging terms. - This means that -\begin_inset Formula $a$ -\end_inset - - must be a multiple of -\begin_inset Formula $p$ -\end_inset - -. - Then, -\begin_inset Formula -\begin{align*} -X_{e} & \equiv X_{0}a^{e}+\frac{a^{e}-1}{a-1}c\equiv(a^{e-1}+a^{e-2}+\dots+a+1)c, & \pmod{p^{e}},\\ -X_{e+\lambda} & \equiv X_{0}a^{e+\lambda}+\frac{a^{e+\lambda}-1}{a-1}c\equiv(a^{e-1}+a^{e-2}+\dots+a+1)c, & \pmod{p^{e}}, -\end{align*} - -\end_inset - -since -\begin_inset Formula $a^{e}\equiv0$ -\end_inset - -, - so -\begin_inset Formula $\mu\leq e$ -\end_inset - -. - The value -\begin_inset Formula $\mu=e$ -\end_inset - - is reached when -\begin_inset Formula $(X_{0},a,c)=(1,p,0)$ -\end_inset - -. - Summing up, - the maximum for -\begin_inset Formula $m=p_{1}^{e_{1}}\cdots p_{t}^{e_{t}}$ -\end_inset - - is -\begin_inset Formula $\max\{e_{1},\dots,e_{t}\}$ -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc9[M22] -\end_layout - -\end_inset - -(W. - E. - Thompson.) When -\begin_inset Formula $c=0$ -\end_inset - - and -\begin_inset Formula $m=2^{e}\geq16$ -\end_inset - -, - Theorems B and C say that the period has length -\begin_inset Formula $2^{e-2}$ -\end_inset - - if and only if the multiplier -\begin_inset Formula $a$ -\end_inset - - satisfies -\begin_inset Formula $a\bmod8=3$ -\end_inset - - or -\begin_inset Formula $a\bmod8=5$ -\end_inset - -. - Show that every such sequence is essentially a linear congruential sequence with -\begin_inset Formula $m=2^{e-2}$ -\end_inset - -, - having -\emph on -full -\emph default - period, - in the following sense: -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $X_{n+1}=(4c+1)X_{n}\bmod2^{e}$ -\end_inset - -, - and -\begin_inset Formula $X_{n}=4Y_{n}+1$ -\end_inset - -, - then -\begin_inset Formula -\[ -Y_{n+1}=((4c+1)Y_{n}+c)\bmod2^{e-2}. -\] - -\end_inset - - -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $X_{n+1}=(4c-1)X_{n}\bmod2^{e}$ -\end_inset - -, - and -\begin_inset Formula $X_{n}=((-1)^{n}(4Y_{n}+1))\bmod2^{e}$ -\end_inset - -, - then -\begin_inset Formula -\[ -Y_{n+1}=((1-4c)Y_{n}-c)\bmod2^{e-2}. -\] - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -We start with -\begin_inset Formula $(Y_{n})_{n}$ -\end_inset - - as defined and see that -\begin_inset Formula $(X_{n})_{n}$ -\end_inset - - calculated from there matches the initial definition of -\begin_inset Formula $(X_{n})_{n}$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -We have -\begin_inset Formula $Y_{n}=\left((4c+1)^{n}Y_{0}+\frac{(4c+1)^{n}-1}{4\cancel{c}}\cancel{c}\right)\bmod2^{e-2}$ -\end_inset - -, - so -\begin_inset Formula -\[ -4Y_{n}+1\equiv(4Y_{0}+1)(4c+1)^{n}\equiv(4c+1)^{n}X_{0}\equiv X_{n}\pmod{2^{e}}. -\] - -\end_inset - - -\end_layout - -\begin_layout Enumerate -We have -\begin_inset Formula $Y_{n}=\left((1-4c)^{n}Y_{0}-\frac{(1-4c)^{n}-1}{-4c}c\right)\bmod2^{e-2}$ -\end_inset - -, - so -\begin_inset Formula -\begin{multline*} -(-1)^{n}(4Y_{n}+1)\equiv(-1)^{n}\left(4(1-4c)^{n}Y_{0}+(1-4c)^{n}\right)=(4Y_{0}+1)(4c-1)^{n}=\\ -=(4c-1)^{n}X_{0}\equiv X_{n+1}\pmod{2^{e}}. -\end{multline*} - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc16[M24] -\end_layout - -\end_inset - - -\emph on -(Existence of primitive roots.) -\emph default - Let -\begin_inset Formula $p$ -\end_inset - - be a prime number. -\end_layout - -\begin_layout Enumerate -Consider the polynomial -\begin_inset Formula $f(x)=x^{n}+c_{1}x^{n-1}+\dots+c_{n}$ -\end_inset - -, - where the -\begin_inset Formula $c$ -\end_inset - -'s are integers. - Given that -\begin_inset Formula $a$ -\end_inset - - is an integer for which -\begin_inset Formula $f(a)\equiv0\pmod p$ -\end_inset - -, - show that there exists a polynomial -\begin_inset Formula -\[ -q(x)=x^{n-1}+q_{1}x^{n-2}+\dots+q_{n-1} -\] - -\end_inset - -with integer coefficients such that -\begin_inset Formula $f(x)\equiv(x-a)q(x)\pmod p$ -\end_inset - - for all integers -\begin_inset Formula $x$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -Let -\begin_inset Formula $f(x)$ -\end_inset - - be a polynomial as in (1). - Show that -\begin_inset Formula $f(x)$ -\end_inset - - has at most -\begin_inset Formula $n$ -\end_inset - - distinct -\begin_inset Quotes eld -\end_inset - -roots -\begin_inset Quotes erd -\end_inset - - modulo -\begin_inset Formula $p$ -\end_inset - -; - that is, - there are at most -\begin_inset Formula $n$ -\end_inset - - integers -\begin_inset Formula $a$ -\end_inset - -, - with -\begin_inset Formula $0\leq a<p$ -\end_inset - -, - such that -\begin_inset Formula $f(a)\equiv0\pmod p$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -Because of exercise 15(2), - the polynomial -\begin_inset Formula $f(x)=x^{\lambda(p)}-1$ -\end_inset - - has -\begin_inset Formula $p-1$ -\end_inset - - distinct roots; - hence there is an integer -\begin_inset Formula $a$ -\end_inset - - with order -\begin_inset Formula $p-1$ -\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 -It suffices to prove that, - for -\begin_inset Formula $f\in\mathbb{Z}_{p}[X]$ -\end_inset - - and -\begin_inset Formula $a\in\mathbb{Z}_{p}$ -\end_inset - - with -\begin_inset Formula $f(a)=0$ -\end_inset - -, - there exists -\begin_inset Formula $q\in\mathbb{Z}_{p}[X]$ -\end_inset - - such that -\begin_inset Formula $f(x)\equiv(x-a)q(x)$ -\end_inset - -, - since then, - for -\begin_inset Formula $f$ -\end_inset - - to have degree -\begin_inset Formula $n$ -\end_inset - - and leading coefficient 1, - -\begin_inset Formula $q$ -\end_inset - - must have degree -\begin_inset Formula $n-1$ -\end_inset - - and leading coefficient -\begin_inset Formula $q$ -\end_inset - -. - This is immediate for -\begin_inset Formula $f=0$ -\end_inset - -, - so we prove it by induction on the degree -\begin_inset Formula $n\geq0$ -\end_inset - - of -\begin_inset Formula $f$ -\end_inset - -. - If -\begin_inset Formula $n=0$ -\end_inset - -, - -\begin_inset Formula $f(a)=c_{0}\neq0\#$ -\end_inset - -, - so this follows trivially. - If -\begin_inset Formula $n>0$ -\end_inset - -, - let -\begin_inset Formula $g(x)\coloneqq f(x)-c_{0}(x-a)x^{n-1}$ -\end_inset - - is a polynomial of degree -\begin_inset Formula $n-1$ -\end_inset - - such that -\begin_inset Formula $g(a)=f(a)=0$ -\end_inset - -, - so by induction there exists -\begin_inset Formula $r\in\mathbb{Z}_{p}(x)$ -\end_inset - - with -\begin_inset Formula $g(x)=(x-a)r(x)$ -\end_inset - -. - But then -\begin_inset Formula $f(x)=g(x)+c_{0}(x-a)x^{n-1}=(x-a)(r(x)+c_{0}x^{n-1})$ -\end_inset - -. - Note that this proof is valid even when changing -\begin_inset Formula $\mathbb{Z}_{p}$ -\end_inset - - to any other domain. -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $a$ -\end_inset - - and -\begin_inset Formula $b$ -\end_inset - - are different roots of -\begin_inset Formula $f$ -\end_inset - -, - then -\begin_inset Formula $f(x)=(x-a)q(x)$ -\end_inset - - for some -\begin_inset Formula $q\in\mathbb{Z}_{p}[X]$ -\end_inset - -, - and -\begin_inset Formula $b$ -\end_inset - - is still a root of -\begin_inset Formula $q$ -\end_inset - - as, - if it wasn't, - it wouldn't be a root of -\begin_inset Formula $f$ -\end_inset - - either. - Therefore, - by induction, - a polynomial -\begin_inset Formula $f\in\mathbb{Z}_{p}[X]\setminus0$ -\end_inset - - with -\begin_inset Formula $n$ -\end_inset - - different roots has at least degree -\begin_inset Formula $n$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -Yes. - Trivial. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc20[M24] -\end_layout - -\end_inset - -(G. - Marsaglia.) The purpose of this exercise is to study the period length of an -\emph on -arbitrary -\emph default - linear congruential sequence. - Let -\begin_inset Formula $Y_{n}=1+a+\dots+a^{n-1}$ -\end_inset - -, - so that -\begin_inset Formula $X_{n}=(AY_{n}+X_{0})\bmod m$ -\end_inset - - for some constant -\begin_inset Formula $A$ -\end_inset - - by Eq. - 3.2.1–(8). -\end_layout - -\begin_layout Enumerate -Prove that the period length of -\begin_inset Formula $\langle X_{n}\rangle$ -\end_inset - - is the period length of -\begin_inset Formula $\langle Y_{n}\bmod m'\rangle$ -\end_inset - -, - where -\begin_inset Formula $m'=m/\gcd(A,m)$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -Prove that the period length of -\begin_inset Formula $\langle Y_{n}\bmod p^{e}\rangle$ -\end_inset - - satisfies the following when -\begin_inset Formula $p$ -\end_inset - - is prime: -\end_layout - -\begin_deeper -\begin_layout Enumerate -If -\begin_inset Formula $a\bmod p=0$ -\end_inset - -, - it is 1. -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $a\bmod p=1$ -\end_inset - -, - it is -\begin_inset Formula $p^{e}$ -\end_inset - -, - except when -\begin_inset Formula $p=2$ -\end_inset - - and -\begin_inset Formula $e\geq2$ -\end_inset - - and -\begin_inset Formula $a\bmod4=3$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $p=2$ -\end_inset - -, - -\begin_inset Formula $e\geq2$ -\end_inset - -, - and -\begin_inset Formula $a\bmod4=3$ -\end_inset - -, - it is twice the order of -\begin_inset Formula $a$ -\end_inset - - modulo -\begin_inset Formula $p^{e}$ -\end_inset - - (see exercise 11), - unless -\begin_inset Formula $a\equiv-1\pmod{2^{e}}$ -\end_inset - - when it is 2. -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $a\bmod p>1$ -\end_inset - -, - it is the order of -\begin_inset Formula $a$ -\end_inset - - modulo -\begin_inset Formula $p^{e}$ -\end_inset - -. -\end_layout - -\end_deeper -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Enumerate -\begin_inset Formula -\[ -X_{n}=X_{n+m}\iff AY_{n}\equiv AY_{n+m}\pmod m\iff Y_{n}\equiv Y_{n+m}\pmod{m'}. -\] - -\end_inset - -Note that -\begin_inset Formula $\langle Y_{n}\bmod t\rangle$ -\end_inset - -, - -\begin_inset Formula $t\in\mathbb{Z}^{+}$ -\end_inset - -, - is the linear congruential sequence with -\begin_inset Formula $Y_{0}=0$ -\end_inset - -, - -\begin_inset Formula $c=1$ -\end_inset - -, - -\begin_inset Formula $a=a$ -\end_inset - -, - and -\begin_inset Formula $m=t$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -\begin_inset Note Note -status open - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_deeper -\begin_layout Enumerate -For -\begin_inset Formula $n\geq e-1$ -\end_inset - -, - -\begin_inset Formula $Y_{n}=(1+a+a^{2}+\dots+a^{e-1})\bmod p$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -Then we're in the conditions of Theorem A. -\end_layout - -\begin_layout Enumerate -If -\begin_inset Formula $e=2$ -\end_inset - -, - then -\begin_inset Formula $a\equiv-1\pmod 4$ -\end_inset - - and this part doesn't apply, - so we assume -\begin_inset Formula $e>2$ -\end_inset - -. - Let -\begin_inset Formula $\lambda$ -\end_inset - - be the order of -\begin_inset Formula $a$ -\end_inset - - modulo -\begin_inset Formula $2^{e}$ -\end_inset - -, - obviously -\begin_inset Formula $\lambda>1$ -\end_inset - -, - so -\begin_inset Formula -\begin{multline*} -Y_{k}=1+a+\dots+a^{k-1}=\frac{a^{k}-1}{a-1}\equiv Y_{0}=0\pmod{2^{e}}\iff\\ -\iff a^{k}-1\equiv0\pmod{2^{e}(a-1)}\iff2^{e}(a-1)\mid a^{k}-1. -\end{multline*} - -\end_inset - -The order -\begin_inset Formula $\lambda$ -\end_inset - - of -\begin_inset Formula $a$ -\end_inset - - modulo -\begin_inset Formula $2^{e}$ -\end_inset - - is the smallest number such that -\begin_inset Formula $2^{e}\mid a^{k}-1$ -\end_inset - -, - and in fact -\begin_inset Formula -\[ -2^{e}\mid a^{k}-1\iff a^{k}\equiv1\pmod{2^{e}}\iff\lambda\mid k. -\] - -\end_inset - -Exercise 11 gives us an unique -\begin_inset Formula $f>1$ -\end_inset - - such that -\begin_inset Formula $a\bmod2^{f+1}=2^{f}\pm1$ -\end_inset - -, - and then says that -\begin_inset Formula $\lambda=2^{e-f}$ -\end_inset - -. - This can be used to prove that -\begin_inset Formula $a^{\lambda}-1$ -\end_inset - - is not a multiple of -\begin_inset Formula $2^{e}(a-1)$ -\end_inset - -, - as if this were the case, - then -\begin_inset Formula $a^{\lambda-1}$ -\end_inset - - would be a multiple of -\begin_inset Formula $2^{e+1}$ -\end_inset - - because -\begin_inset Formula $a-1$ -\end_inset - - is even, - but by Exercise 11 the order of -\begin_inset Formula $a$ -\end_inset - - modulo -\begin_inset Formula $e+1$ -\end_inset - - is -\begin_inset Formula $2^{e+1-f}>\lambda\#$ -\end_inset - -. - However, - since -\begin_inset Formula $a^{\lambda}-1$ -\end_inset - - is a multiple of both -\begin_inset Formula $2^{e}$ -\end_inset - - and -\begin_inset Formula $a^{\lambda}-1$ -\end_inset - -, - it is a multiple of -\begin_inset Formula $\text{lcm}\{2^{e},a^{\lambda}-1\}=\frac{2^{e}(a^{\lambda}-1)}{2}$ -\end_inset - - and therefore -\begin_inset Formula $a^{2\lambda}-1=(a^{\lambda}-1)(a^{\lambda}+1)=(a^{\lambda}-1)^{2}+2(a^{\lambda}-1)$ -\end_inset - - is a multiple of -\begin_inset Formula $2^{e}(a^{\lambda}-1)$ -\end_inset - -. -\end_layout - -\begin_layout Enumerate -Like before, - -\begin_inset Formula $Y_{k}\equiv0\pmod{2^{e}}\iff p^{e}(a-1)\mid a^{k}-1$ -\end_inset - -. - This time, - however, - -\begin_inset Formula $\gcd\{a-1,p^{e}\}=1$ -\end_inset - -, - so -\begin_inset Formula $p^{e}(a-1)\mid a^{k}-1\iff p^{e},a-1\mid a^{k}-1\iff p^{e}\mid a^{k}-1$ -\end_inset - -, - and the lowest -\begin_inset Formula $k$ -\end_inset - - for which this happens is precisely the order of -\begin_inset Formula $a$ -\end_inset - - modulo -\begin_inset Formula $p^{e}$ -\end_inset - -. -\end_layout - -\end_deeper -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc22[M25] -\end_layout - -\end_inset - -Discuss the problem of finding moduli -\begin_inset Formula $m=b^{k}\pm b^{l}\pm1$ -\end_inset - - so that the subtract-with-borrow and add-with-carry generators of exercise 3.2.1.1–14 will have very long periods. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -First we would need the prime factorization of -\begin_inset Formula $m$ -\end_inset - -, - which is not easily characterized from -\begin_inset Formula $b$ -\end_inset - -, - -\begin_inset Formula $k$ -\end_inset - -, - and -\begin_inset Formula $l$ -\end_inset - -. - Once we have that we may apply Theorems A–C. - The solution in the book suggests looking for -\begin_inset Formula $m$ -\end_inset - - to be prime. -\end_layout - -\end_body -\end_document |
