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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 /2.3.4.3.lyx | |
| parent | 16ccda6c459c0fd7ca2081e9d541124c28b0c556 (diff) | |
Changed layout for more manageable volumes
Diffstat (limited to '2.3.4.3.lyx')
| -rw-r--r-- | 2.3.4.3.lyx | 508 |
1 files changed, 0 insertions, 508 deletions
diff --git a/2.3.4.3.lyx b/2.3.4.3.lyx deleted file mode 100644 index 44b134e..0000000 --- a/2.3.4.3.lyx +++ /dev/null @@ -1,508 +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 Note Note -status open - -\begin_layout Plain Layout -TODO 1, - 3, - 6 (2pp., - 0:46) -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc1[M10] -\end_layout - -\end_inset - -The text refers to a set -\begin_inset Formula $S$ -\end_inset - - containing finite sequences of positive integers, - and states that this set is -\begin_inset Quotes eld -\end_inset - -essentially an oriented tree. -\begin_inset Quotes erd -\end_inset - - What is the root of this oriented tree, - and what are the arcs? -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -The vertices are the elements of -\begin_inset Formula $S$ -\end_inset - -, - the root is -\begin_inset Formula $\emptyset$ -\end_inset - -, - and the arcs go from -\begin_inset Formula $(x_{1},\dots,x_{n})$ -\end_inset - - to -\begin_inset Formula $(x_{1},\dots,x_{n-1})$ -\end_inset - -, - for every -\begin_inset Formula $(x_{1},\dots,x_{n})\in S\setminus\{\emptyset\}$ -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc3[M23] -\end_layout - -\end_inset - -If it is possible to tile the upper right quadrant of the plane when given an -\emph on -infinite -\emph default - set of tetrad types, - is it always possible to tile the whole plane? -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -No. - For example, - our tiles might be of the form -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -begin{center} -\end_layout - -\begin_layout Plain Layout - - -\backslash -begin{tikzpicture} -\end_layout - -\begin_layout Plain Layout - - -\backslash -draw (0,0) -- (0,2) -- (2,2) -- (2,0) -- (0,0) -- (2,2) -\end_layout - -\begin_layout Plain Layout - - (0,2) -- (2,0) -\end_layout - -\begin_layout Plain Layout - - (0.5,1) node{$n$} (1,0.5) node{$n$} -\end_layout - -\begin_layout Plain Layout - - (1.5,1) node{$n+1$} (1,1.5) node{$n+1$}; -\end_layout - -\begin_layout Plain Layout - - -\backslash -end{tikzpicture} -\end_layout - -\begin_layout Plain Layout - - -\backslash -end{center} -\end_layout - -\end_inset - -for -\begin_inset Formula $n\in\mathbb{N}$ -\end_inset - -. - Then in the -\begin_inset Formula $(x,y)$ -\end_inset - - square we might place the tile with -\begin_inset Formula $n=\max\{x,y\}$ -\end_inset - - and this would tile the upper right quadrant, - but there's obviously no way to tile the whole plane. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -rexerc6[M23] -\end_layout - -\end_inset - -(Otto Schreier.) In a famous paper, - B. - L. - van der Waerden proved the following theorem: -\end_layout - -\begin_layout Quote - -\shape slanted -If -\begin_inset Formula $k$ -\end_inset - - and -\begin_inset Formula $m$ -\end_inset - - are positive integers, - and if we have -\begin_inset Formula $k$ -\end_inset - - sets -\begin_inset Formula $S_{1},\dots,S_{k}$ -\end_inset - - of positive integers with every positive integer included in at least one of these sets, - then at least of the sets -\begin_inset Formula $S_{j}$ -\end_inset - - contains an arithmetic progression of length -\begin_inset Formula $m$ -\end_inset - -. -\end_layout - -\begin_layout Standard -(The latter statement means there exist integers -\begin_inset Formula $a$ -\end_inset - - and -\begin_inset Formula $\delta>0$ -\end_inset - - such that -\begin_inset Formula $a+\delta$ -\end_inset - -, - -\begin_inset Formula $a+2\delta$ -\end_inset - -, - ..., - -\begin_inset Formula $a+m\delta$ -\end_inset - - are all in -\begin_inset Formula $S_{j}$ -\end_inset - -.) If possible, - use this result and the infinity lemma to prove the following stronger statement: -\end_layout - -\begin_layout Quote - -\shape slanted -If -\begin_inset Formula $k$ -\end_inset - - and -\begin_inset Formula $m$ -\end_inset - - are positive integers, - there is a number -\begin_inset Formula $N$ -\end_inset - - such that if we have -\begin_inset Formula $k$ -\end_inset - - sets -\begin_inset Formula $S_{1},\dots,S_{k}$ -\end_inset - - of integers with every integer between 1 and -\begin_inset Formula $N$ -\end_inset - - included in at least one of these sets, - then at least one of the sets -\begin_inset Formula $S_{j}$ -\end_inset - - contains an arithmetic progression of length -\begin_inset Formula $m$ -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -answer -\end_layout - -\end_inset - -It is enough to prove it when the set that contains every integer between 1 and -\begin_inset Formula $N$ -\end_inset - - is -\begin_inset Formula $S_{1}$ -\end_inset - -. - We define a tree whose vertices are the tuples -\begin_inset Formula $(S_{1},\dots,S_{k})$ -\end_inset - - of finite sets of integers such that, - if -\begin_inset Formula $n=\max\bigcup_{i=1}^{k}S_{i}$ -\end_inset - -, - every positive integer up to -\begin_inset Formula $n$ -\end_inset - - is in one of the sets, - and such that no set contains an arithmetic progression of length -\begin_inset Formula $m$ -\end_inset - -. - The edges go from one such tuple to -\begin_inset Formula $(S_{1}\setminus\{n\},\dots,S_{k}\setminus\{n\})$ -\end_inset - -, - so the root is -\begin_inset Formula $(\emptyset,\dots,\emptyset)$ -\end_inset - - and -\begin_inset Formula $n$ -\end_inset - - is the height of the node in the tree. -\end_layout - -\begin_layout Standard -Since each vertex contains a finite number of children ( -\begin_inset Formula $2^{k}-1$ -\end_inset - -, - corresponding to the ways of adding the next number to one or more of the sets), - it follows that if this tree were infinite, - there would be an infinite path. - By van der Waerden theorem, - the component-wise union of this path would give us a tuple -\begin_inset Formula $(S_{1},\dots,S_{k})$ -\end_inset - - such that some -\begin_inset Formula $S_{j}$ -\end_inset - - contains an arithmetic progression of length -\begin_inset Formula $m$ -\end_inset - -, - so by construction one of the nodes in the path would follow this condition. -\begin_inset Formula $\#$ -\end_inset - - -\end_layout - -\begin_layout Standard -Thus the tree is finite and we just need to take -\begin_inset Formula $N$ -\end_inset - - as one plus the depth of the tree. -\end_layout - -\end_body -\end_document |
