Forever young

• Notation
  • 1. Math Symbols
  • 2. Logic Symbols
  • 3. Computer Symbols
• Folders with clear dependencies
• 友链

Notation

1. Math Symbols

• Vector is denoted as bold lowercase letter, e.g. $\mathbf{a}$, Matrix is denoted as bold capital letter, e.g. $\mathbf{A}$, $a_i$ means the $i$th element of $\mathbf{a}$, $a_{ij}$ means the $(i,j)$th element of $\mathbf{A}$
• All vectors are column vectors
• $\mathbb{Z}$ is the set of integers.
• $\mathbb{Q}$ is the set of rational numbers.
• $\mathbb{R}$ is the set of real numbers.
• $\mathbb{C}$ is the set of complex numbers.
• $\mathbb{F}$ is a filtration.
• $\mathbb{P}$ is a probability measure.
• $\mathbb{E}$ is the expectation operator.
• $[n]$ := $\{1,2,\cdots ,n\}$
• ${\mathbb{Z}}_n$ := $\{0,1,\cdots ,n-1\}$
• ${\mathbb{Z}}_{\ge n}$ := $\{i\mid i\in \mathbb{Z}\wedge i\ge n\}$
• $\overline{\mathbb{R}}$ := $\mathbb{R}\cup \{-\infty ,+\infty \}$
• For $X\subseteq \overline{\mathbb{R}}$, $X^{+}$ := $\{x\in X|x>0\}$
• For $X\subseteq \overline{\mathbb{R}}$, $X^{\ast }$ := $\{x\in X|x\ge 0\}$
• For $\mathbf{a},\mathbf{b}\in {\overline{\mathbb{R}}}^n,\mathbf{a}\le \mathbf{b}$ := $\forall i,a_i\le b_i$
• Class of sets is denoted as calligraphic letter, e.g. $\mathcal{A}$, $\mathcal{B}$, $\mathcal{F}$
• $\mathcal{P}(X)$ is the power set of $X$
• $⨄$ represents the union of disjoint sets.
• $A^{\text{\#}}$ is the adjoint matrix of $A$
• $(X,\tau )$ is a topological space, briefly written as $X$
• $\mathcal{B}(X):=\sigma (\tau )$, where $(X,\tau )$ is a topological space
• $\wedge$ represents the and for logic, min for function
• $\vee$ represents the or for logic, max for function
• $A:=B$ 表示 $A$ 被定义为 $B$
• $A=:B$ 表示 $A$ 被记作 $B$
• ${\nabla }_{\mathbf{x}}\varphi (\mathbf{x})$ or $\nabla \varphi (\mathbf{x})$: 标量值函数 $\nabla \varphi (\mathbf{x})$ 的梯度
• $\nabla \cdot \varphi (\mathbf{x})$: $\varphi :{\mathbb{R}}^d\to {\mathbb{R}}^d$ 的散度
• $\nabla \cdot \varphi (\mathbf{x})$: $\varphi :{\mathbb{R}}^d\to {\mathbb{R}}^{d\times d}$ 逐行散度所组成的列向量

2. Logic Symbols

• Little letters (e.g. $p,q,r$) are used to represent propostional variables
• $\neg$ is used to represent negation
• $\wedge$ is used to represent conjunction
• $\vee$ is used to represent disjunction
• $\to$ is used to represent implication
• $⟺$ is used to represent equivalence
• $\mathcal{A}⟹\mathcal{B}$ means $(\mathcal{A}\to \mathcal{B})$ is True
• $\mathcal{A}⟺\mathcal{B}$ means $((\mathcal{A}\to \mathcal{B})\wedge (\mathcal{B}\to \mathcal{A}))$ is True
• ${\mathcal{L}}_0$ is used to represent a zero-order language
• $\mathcal{L}$ is used to represent a first-order language
• mathscr upper letters (e.g. $\mathcal{A},\mathcal{B},\mathcal{C}$) are used to represent the formulas (well-formed formulas,wfs) of a language $\mathcal{L}$ and ${\mathcal{L}}_0$

3. Computer Symbols

• Local network is denoted as capital letter, e.g. $A$,$B$,$C$
• Host in local network is denoted as small letter, e.g. $a$,$b$,$c$ located in local network $A$,$B$,$C$
• Public ip is denoted as Greek letter, e.g. $\alpha$,$\gamma$,$\beta$
• Hosts in the same local network are distinguished by subscripts, e.g. $a_1$,$a_2$,$a_5$ located in local network $A$.

Folders with clear dependencies

• linear-algebra
• 数学分析
• 抽象代数
• 数理逻辑
• 朴素集合论
• 测度论与概率论
• 点集拓扑

友链

友链

名称	链接
virgiling	https://virgiling.wiki/

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