這是英文版實分析裡的一句話,請大佬解釋一下句子的意思和結構?
A basic result of the theory is the existence (and uniqueness) of such a measure, Lebesgue measure, when one limits oneself to a class of reasonable sets, those which are “measurable。”
1。when是時間狀語嗎?
2。這句話在說啥?邏輯是啥?什麼叫當限制在合理的可測集時就產生了勒貝格測度啊?
A basic result of the theory is the existence (and uniqueness) of such a measure, Lebesgue measure, when one limits oneself to a class of reasonable sets, those which are “measurable。”
the existence (and uniqueness) of such a measure:存在著這樣一種measure
of: (用於由動詞轉化的名詞之後,of之後的名詞可以是受動者,也可以是施動者)
used after nouns formed from verbs。 The noun after ‘of’ can be either the object or the subject of the action。
the arrival of the police (= they arrive)
警察的到來
criticism of the police (= they are criticized)
對警察的批評
fear of the dark
對黑暗的懼怕
the howling of the wind
狂風的呼嘯
the existence (and uniqueness) of such a measure, Lebesgue measure:
這裡的Lebesgure measure與a measure是同位語關係,相當於是一個插入語,用於補充說明a measure是一個什麼樣的measure。因些,將“, Lebesgure measure,”刪掉並不會影響語義的完整。故題主的引文可壓縮成“A basic result of the theory is the existence (and uniqueness) of such a measure when one limits oneself to a class of reasonable sets, those which are “measurable。””
同樣的, those which are ‘measurable’也是一個插入語,這個插入語有可能修飾oneself,也可能修飾a class of reasonable sets。因為這裡沒有更多的背景資料,沒辦法判斷出one指代的是什麼,所以這裡就不下結論。但不論如何,插入語仍可依據上面的規則,把他刪掉。於是,原引文就更一步的被壓縮成了這樣:“A basic result of the theory is the existence (and uniqueness) of such a measure when one limits oneself to a class of reasonable sets。”
所以,原引文大意就是:這個理論的基本成果就是存在著一種被稱為Lebesgure measure的測量,這個結論的成立條件就是one limits oneself to a class of reasonable sets這個時間點出現的時侯或這個時間點出現之後。
A basic result of the theory is the existence (and uniqueness) of such a measure, Lebesgue measure, when one limits oneself to a class of reasonable sets, those which are “measurable。”
這個理論提供了一個基本結果,就是某種條件下勒貝格測度的存在性(及其唯一性)。
什麼條件呢?
就是隻考慮由reasonable set構成的類,所謂reasonable set,就是可測度的集合。
句子結構很簡單,不需要進行分析。
when就是 當且僅當 的當,根本不需要想那麼多。
最後,這樣學實分析真是勇氣可嘉。
{A {basic {result}} of {the theory}} is {{{the {existence (and uniqueness)} of {such {a measure}}}, Lebesgue measure}, when one {limits oneself to {a class of {{{reasonable {sets}}, {{those} which are “measurable”}}}}}。
reasonable 和中文“合理”的語義不同。
有時候 when = in the circumastance/situation which
也有時候 when = if
這裡說的是the existence and uniqueness of such a measure的條件
一個基本常識是, 對於實數上的閉區間來說, 它有些子集不能被賦予Lebesgue measure, 比如vitali set
注意,non-measurable 條件比 Lebesgue measure exists 的條件弱(Lebesgue measure 有個性質translation invariant)。 雖然並作者沒寫清楚它說的measurable是不是Lebesgue-measurable, 但是從上下文來看他說的就是Lebesgue-measurable
以及,就如同你滿腦子中文漿糊來揣測(而不是查辭典和理解)這句話一樣, 從英文的角度來揣測你題幹中的“邏輯是啥?”, WTF, what do you mean by 邏輯?