計劃進修PhD/Research討論區(27) The brain is wider than the sky

1001 回覆
6 Like 1 Dislike
2017-06-29 13:33:57
想問下咩叫Offer of Tenure - Associate Professor


tenure prof姐係點對哩d 一無所知

2017-06-29 13:34:41



睇咗老婆先生

2017-06-29 13:35:36



睇咗老婆先生


2017-06-29 13:36:00
想問下咩叫Offer of Tenure - Associate Professor


tenure prof姐係點對哩d 一無所知


2017-06-29 13:40:28



睇咗老婆先生



2017-06-29 13:59:54
想問下咩叫Offer of Tenure - Associate Professor


tenure prof姐係點對哩d 一無所知



associate都鐵飯碗

2017-06-29 14:01:50
想問下咩叫Offer of Tenure - Associate Professor


tenure prof姐係點對哩d 一無所知



associate都鐵飯碗


2017-06-29 14:03:41
2017-06-29 14:05:16
想問下咩叫Offer of Tenure - Associate Professor


tenure prof姐係點對哩d 一無所知



associate都鐵飯碗



2017-06-29 14:07:39
http://www.ams.org/journals/bull/2017-54-01/S0273-0979-2016-01552-7/S0273-0979-2016-01552-7.pdf
WHAT ARE LYAPUNOV EXPONENTS, AND WHY ARE THEY INTERESTING?
碌落少少已經唔覺得interesting
2017-06-29 14:10:40
http://www.ams.org/journals/bull/2017-54-01/S0273-0979-2016-01552-7/S0273-0979-2016-01552-7.pdf
WHAT ARE LYAPUNOV EXPONENTS, AND WHY ARE THEY INTERESTING?
碌落少少已經唔覺得interesting

2017-06-29 14:21:53



2017-06-29 14:50:00




2017-06-29 14:51:47





2017-06-29 14:59:31
hea左兩日突然間又新post!
2017-06-29 15:49:29

2017-06-29 18:13:41


2017-06-29 18:17:00



2017-06-29 18:19:42




2017-06-29 18:33:08




2017-06-29 19:28:56
http://www.ams.org/journals/bull/2017-54-01/S0273-0979-2016-01552-7/S0273-0979-2016-01552-7.pdf
WHAT ARE LYAPUNOV EXPONENTS, AND WHY ARE THEY INTERESTING?
碌落少少已經唔覺得interesting

Oseledets's theorem好interesting

不過篇文真係寫得麻麻地冇乜background應該唔太知噏乜

Lyapunov exponent大致上就係睇一個dynamical system平均嘅"expansion rate"有幾快

例如f(x)=2x mod 1,你當依個map係個dynamical system on circle嘅話,你會發現依個map會將啲嘢「放大」(例如將[0,1/2]變做[0,1]

但如果你睇g(x)=3x mod 1,應該唔難想像g expand得快過f

個rate可以話係取決於個slope有幾大,上面嘅例子個slope係constant,所以你可以好隨便咁講f嘅rate係2,g嘅rate係3

不過咁樣會唔夠好,因為dynamical system睇嘅唔單止係f,仲想睇f(f(...f(x))...)嘅behaviour,所以要睇嘅應該係f^n嘅slope

用上面嘅例子,f^n嘅slope係2^n,g^n嘅slope係3^n,依個sequence唔converge,但take完logarithm然後除以n就好好多,分別係log2同log3

但喺一般情況,個map個slope唔會係constant,但你仍然可以consider log|(h^n)'(x)|,你會發現用chain rule後會變咗 sum log|h'(h^i(x))|,如果h係ergodic依個sum除以n會converge to integrate log|h'| over the space,而依個數字就係Lyapunov exponent,話你知h平均expand得幾快

2017-06-29 20:30:52
http://www.ams.org/journals/bull/2017-54-01/S0273-0979-2016-01552-7/S0273-0979-2016-01552-7.pdf
WHAT ARE LYAPUNOV EXPONENTS, AND WHY ARE THEY INTERESTING?
碌落少少已經唔覺得interesting

Oseledets's theorem好interesting

不過篇文真係寫得麻麻地冇乜background應該唔太知噏乜

Lyapunov exponent大致上就係睇一個dynamical system平均嘅"expansion rate"有幾快

例如f(x)=2x mod 1,你當依個map係個dynamical system on circle嘅話,你會發現依個map會將啲嘢「放大」(例如將[0,1/2]變做[0,1]

但如果你睇g(x)=3x mod 1,應該唔難想像g expand得快過f

個rate可以話係取決於個slope有幾大,上面嘅例子個slope係constant,所以你可以好隨便咁講f嘅rate係2,g嘅rate係3

不過咁樣會唔夠好,因為dynamical system睇嘅唔單止係f,仲想睇f(f(...f(x))...)嘅behaviour,所以要睇嘅應該係f^n嘅slope

用上面嘅例子,f^n嘅slope係2^n,g^n嘅slope係3^n,依個sequence唔converge,但take完logarithm然後除以n就好好多,分別係log2同log3

但喺一般情況,個map個slope唔會係constant,但你仍然可以consider log|(h^n)'(x)|,你會發現用chain rule後會變咗 sum log|h'(h^i(x))|,如果h係ergodic依個sum除以n會converge to integrate log|h'| over the space,而依個數字就係Lyapunov exponent,話你知h平均expand得幾快


吹水台自選台熱 門最 新手機台時事台政事台World體育台娛樂台動漫台Apps台遊戲台影視台講故台健康台感情台家庭台潮流台美容台上班台財經台房屋台飲食台旅遊台學術台校園台汽車台音樂台創意台硬件台電器台攝影台玩具台寵物台軟件台活動台電訊台直播台站務台黑 洞