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	<title>Comments on: Could anything like Deolalikar&#8217;s strategy work?</title>
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	<description>Mathematics related discussions</description>
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		<title>By: Micki St James</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-9722</link>
		<dc:creator><![CDATA[Micki St James]]></dc:creator>
		<pubDate>Sun, 12 Sep 2010 07:03:44 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-9722</guid>
		<description><![CDATA[No I can&#039;t translate, sorry.  But www.reverso.net will attempt a
translation if you want to see the current state of automatic on-demand free online translation.
When I tried it I extracted a sentence &quot;In the meantime the reactors found two ( and half ) essential problems with the proof.&quot; but
I have no idea whether that is in any way faithful to the sentiment
actually expressed.]]></description>
		<content:encoded><![CDATA[<p>No I can&#8217;t translate, sorry.  But <a href="http://www.reverso.net" rel="nofollow">http://www.reverso.net</a> will attempt a<br />
translation if you want to see the current state of automatic on-demand free online translation.<br />
When I tried it I extracted a sentence &#8220;In the meantime the reactors found two ( and half ) essential problems with the proof.&#8221; but<br />
I have no idea whether that is in any way faithful to the sentiment<br />
actually expressed.</p>
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		<title>By: palibacsi</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-9611</link>
		<dc:creator><![CDATA[palibacsi]]></dc:creator>
		<pubDate>Fri, 10 Sep 2010 14:36:20 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-9611</guid>
		<description><![CDATA[Can anyone translate the last comment or tell what is stated therein?]]></description>
		<content:encoded><![CDATA[<p>Can anyone translate the last comment or tell what is stated therein?</p>
]]></content:encoded>
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		<title>By: P נגד NP ומדליות פילד. שתי הערות לסדר היום &#124; ניימן 3.0</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-9106</link>
		<dc:creator><![CDATA[P נגד NP ומדליות פילד. שתי הערות לסדר היום &#124; ניימן 3.0]]></dc:creator>
		<pubDate>Sun, 22 Aug 2010 07:57:51 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-9106</guid>
		<description><![CDATA[[...] הפעילות בבלוגים שקקה חיים. ובמתמטיקה המודרנית עיקר הפעילות מתבצעת באינטרנט &#8211; בפוסטים, בפלטפורמות העבודה השונות (נושא שראוי לפוסט בפני עצמו) &#8211; וכמובן: בתגובות. לדעתי, יש כבר אנשים שעובדים על הבעיה מבלי לקרוא את הטיוטה עצמה, אלא ע&quot;פ הידע בפוסטיםתגובות בלבד. בחזית המגיבים עומד, כמעט כמו תמיד בשנים האחרונות, טרנס טאו. שעושה רושם שלח על עצמו את המשימה להתמחות בכל תת-תחום מתמטי. בינתיים המגיבים מצאו שתיים (וחצי) בעיות מהותיות עם ההוכחה. דאולאליקר הגיב לחלקן, בעיקר ע&quot;י כך שאמר שהוא כותב גירסא מלאה, טכנית, שתפורסם בעתיד הקרוב. את המגיבים זה לא סיפק, והם נראים עדיין סקפטים למדי (מה שלא אומר הרבה, היות וכל הכרזה על פתרון בעיה כזאת מחויבת מעצם הגדרת הבעיה להיות מלווה בסקפטיות). מה שבינתיים העביר את הדיון לשאלות מהותיות יותר, כמו &#039;האם האסטרטגיה הכללית של ההוכחה יכולה להיות יעילה?&#039; [...]]]></description>
		<content:encoded><![CDATA[<p>[...] הפעילות בבלוגים שקקה חיים. ובמתמטיקה המודרנית עיקר הפעילות מתבצעת באינטרנט &#8211; בפוסטים, בפלטפורמות העבודה השונות (נושא שראוי לפוסט בפני עצמו) &#8211; וכמובן: בתגובות. לדעתי, יש כבר אנשים שעובדים על הבעיה מבלי לקרוא את הטיוטה עצמה, אלא ע&quot;פ הידע בפוסטיםתגובות בלבד. בחזית המגיבים עומד, כמעט כמו תמיד בשנים האחרונות, טרנס טאו. שעושה רושם שלח על עצמו את המשימה להתמחות בכל תת-תחום מתמטי. בינתיים המגיבים מצאו שתיים (וחצי) בעיות מהותיות עם ההוכחה. דאולאליקר הגיב לחלקן, בעיקר ע&quot;י כך שאמר שהוא כותב גירסא מלאה, טכנית, שתפורסם בעתיד הקרוב. את המגיבים זה לא סיפק, והם נראים עדיין סקפטים למדי (מה שלא אומר הרבה, היות וכל הכרזה על פתרון בעיה כזאת מחויבת מעצם הגדרת הבעיה להיות מלווה בסקפטיות). מה שבינתיים העביר את הדיון לשאלות מהותיות יותר, כמו &#039;האם האסטרטגיה הכללית של ההוכחה יכולה להיות יעילה?&#039; [...]</p>
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		<title>By: Bhupinder Singh Anand</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8849</link>
		<dc:creator><![CDATA[Bhupinder Singh Anand]]></dc:creator>
		<pubDate>Mon, 16 Aug 2010 05:07:26 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8849</guid>
		<description><![CDATA[Deolalikar&#039;s attempt to define the class P precisely in terms of FO formulas can also be seen as part of a serious attempt to bridge computability and provability.

Although not immediately obvious, the roots of the PvNP problem may lie in how we define the satisfiability of the atomic formulas of the first order arithmetic PA under an interpretation (following Tarski&#039;s inductive definitions of the satisfaction, and truth, of the formulas of a formal language under an interpretation).

For instance, if an n-ary atomic formula [f(x1, x2, ..., xn)] of PA interprets under the standard interpretation I_Standard of PA over the domain N of the natural numbers as the arithmetical relation f(x1, x2, ..., xn), and the PA numeral [ai] as the natural number ai, then [f(x1, x2, ..., xn)] is defined as satisfied under I_Standard for any given sequence of numerals [a1, a2, ..., an] if, and only if, f(x1, x2, ..., xn) is effectively verifiable instantiationally over N, and f(a1, a2, ..., an) holds for the natural number sequence (a1, a2, ..., an).

(See Lemmas 16 &amp; 17 in the link below.) 

There is, however, an alternative interpretation I_Algorithmic of PA over N where, if an n-ary atomic formula [f(x1, x2, ..., xn)] of PA interprets under I_Algorithmic as the arithmetical relation f(x1, x2, ..., xn), and the numeral [ai] as the natural number ai, then [f(x1, x2, ..., xn)] is defined as satisfied under I_Algorithmic for any given sequence of numerals [a1, a2, ..., an] if, and only if, f(x1, x2, ..., xn) is effectively computable (decidable) algorithmically over N, and f(a1, a2, ..., an) holds for the natural number sequence (a1, a2, ..., an).

(See Lemma 18 in the link below.) 

Now, it can be argued that the interpretation I_Algorithmic is sound; and that a PA formula [f] is provable if, and only if, f interprets under I_Algorithmic as an arithmetical relation that is effectively computable (decidable) algorithmically as always true over N.

(See Theorems 4 &amp; 6 in the link below.)

This could be the bridge that Deolalikar appears to be implicitly seeking by his argumentation since, in view of Goedel&#039;s construction of a PA formula that is PA-unprovable but effectively verifiable as always true over N, it would immediately follow that P=/=NP (irrespective, however, of the precise definitions of the classes P and NP).

(See Theorem 7 in the link below.)

http://alixcomsi.com/27_Resolving_PvNP_Update.pdf]]></description>
		<content:encoded><![CDATA[<p>Deolalikar&#8217;s attempt to define the class P precisely in terms of FO formulas can also be seen as part of a serious attempt to bridge computability and provability.</p>
<p>Although not immediately obvious, the roots of the PvNP problem may lie in how we define the satisfiability of the atomic formulas of the first order arithmetic PA under an interpretation (following Tarski&#8217;s inductive definitions of the satisfaction, and truth, of the formulas of a formal language under an interpretation).</p>
<p>For instance, if an n-ary atomic formula [f(x1, x2, ..., xn)] of PA interprets under the standard interpretation I_Standard of PA over the domain N of the natural numbers as the arithmetical relation f(x1, x2, &#8230;, xn), and the PA numeral [ai] as the natural number ai, then [f(x1, x2, ..., xn)] is defined as satisfied under I_Standard for any given sequence of numerals [a1, a2, ..., an] if, and only if, f(x1, x2, &#8230;, xn) is effectively verifiable instantiationally over N, and f(a1, a2, &#8230;, an) holds for the natural number sequence (a1, a2, &#8230;, an).</p>
<p>(See Lemmas 16 &amp; 17 in the link below.) </p>
<p>There is, however, an alternative interpretation I_Algorithmic of PA over N where, if an n-ary atomic formula [f(x1, x2, ..., xn)] of PA interprets under I_Algorithmic as the arithmetical relation f(x1, x2, &#8230;, xn), and the numeral [ai] as the natural number ai, then [f(x1, x2, ..., xn)] is defined as satisfied under I_Algorithmic for any given sequence of numerals [a1, a2, ..., an] if, and only if, f(x1, x2, &#8230;, xn) is effectively computable (decidable) algorithmically over N, and f(a1, a2, &#8230;, an) holds for the natural number sequence (a1, a2, &#8230;, an).</p>
<p>(See Lemma 18 in the link below.) </p>
<p>Now, it can be argued that the interpretation I_Algorithmic is sound; and that a PA formula [f] is provable if, and only if, f interprets under I_Algorithmic as an arithmetical relation that is effectively computable (decidable) algorithmically as always true over N.</p>
<p>(See Theorems 4 &amp; 6 in the link below.)</p>
<p>This could be the bridge that Deolalikar appears to be implicitly seeking by his argumentation since, in view of Goedel&#8217;s construction of a PA formula that is PA-unprovable but effectively verifiable as always true over N, it would immediately follow that P=/=NP (irrespective, however, of the precise definitions of the classes P and NP).</p>
<p>(See Theorem 7 in the link below.)</p>
<p><a href="http://alixcomsi.com/27_Resolving_PvNP_Update.pdf" rel="nofollow">http://alixcomsi.com/27_Resolving_PvNP_Update.pdf</a></p>
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	<item>
		<title>By: gowers</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8472</link>
		<dc:creator><![CDATA[gowers]]></dc:creator>
		<pubDate>Sat, 14 Aug 2010 07:03:08 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8472</guid>
		<description><![CDATA[That was a piece of absent-mindedness on my part. Many thanks for pointing it out -- I have now added Rudich&#039;s name to the sentence in question.]]></description>
		<content:encoded><![CDATA[<p>That was a piece of absent-mindedness on my part. Many thanks for pointing it out &#8212; I have now added Rudich&#8217;s name to the sentence in question.</p>
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		<title>By: David Feldman</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8468</link>
		<dc:creator><![CDATA[David Feldman]]></dc:creator>
		<pubDate>Sat, 14 Aug 2010 06:21:26 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8468</guid>
		<description><![CDATA[Why cite only Razbarov for inventing the natural proofs barrier?]]></description>
		<content:encoded><![CDATA[<p>Why cite only Razbarov for inventing the natural proofs barrier?</p>
]]></content:encoded>
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	<item>
		<title>By: Jay Sulzberger</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8430</link>
		<dc:creator><![CDATA[Jay Sulzberger]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 22:25:15 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8430</guid>
		<description><![CDATA[Oi, here is, I hope, right address:

http://www.panix.com/~jays/Boole.four.page.summary.for.1.August.2006.Cork.conference.Sulzberger.v.5.pdf

Please forgive repetition!]]></description>
		<content:encoded><![CDATA[<p>Oi, here is, I hope, right address:</p>
<p><a href="http://www.panix.com/~jays/Boole.four.page.summary.for.1.August.2006.Cork.conference.Sulzberger.v.5.pdf" rel="nofollow">http://www.panix.com/~jays/Boole.four.page.summary.for.1.August.2006.Cork.conference.Sulzberger.v.5.pdf</a></p>
<p>Please forgive repetition!</p>
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	<item>
		<title>By: Jay Sulzberger</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8429</link>
		<dc:creator><![CDATA[Jay Sulzberger]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 22:22:52 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8429</guid>
		<description><![CDATA[Oi, here is I hope address:

http://www.panix.com/~jays/Boole.four.page.summary.for.1.August.2006.Cork.conference.Sulzberger.pdf

Please forgive pleonastic repetition!]]></description>
		<content:encoded><![CDATA[<p>Oi, here is I hope address:</p>
<p><a href="http://www.panix.com/~jays/Boole.four.page.summary.for.1.August.2006.Cork.conference.Sulzberger.pdf" rel="nofollow">http://www.panix.com/~jays/Boole.four.page.summary.for.1.August.2006.Cork.conference.Sulzberger.pdf</a></p>
<p>Please forgive pleonastic repetition!</p>
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		<title>By: Jay Sulzberger</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8426</link>
		<dc:creator><![CDATA[Jay Sulzberger]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 22:11:18 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8426</guid>
		<description><![CDATA[I believe Deolalikar&#039;s lowness in the space of graphical models property holds.  Deolalikar&#039;s attempt takes account of a known difficulty, which encourages me to think that Deolalikar is in command of the main insight here, even though this particular proof of the lowness property may fail. The sort of lowness property I have in mind does not hold of your random circuit. I hope to put out a note before a decade^Wyear on this.]]></description>
		<content:encoded><![CDATA[<p>I believe Deolalikar&#8217;s lowness in the space of graphical models property holds.  Deolalikar&#8217;s attempt takes account of a known difficulty, which encourages me to think that Deolalikar is in command of the main insight here, even though this particular proof of the lowness property may fail. The sort of lowness property I have in mind does not hold of your random circuit. I hope to put out a note before a decade^Wyear on this.</p>
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		<title>By: Terence Tao</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8405</link>
		<dc:creator><![CDATA[Terence Tao]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 18:32:34 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8405</guid>
		<description><![CDATA[Over at Dick&#039;s blog, &lt;a HREF=&quot;http://rjlipton.wordpress.com/2010/08/12/fatal-flaws-in-deolalikars-proof/#comment-5326&quot; rel=&quot;nofollow&quot;&gt;Jun Tarui&lt;/A&gt; points out that I may have oversimplified somewhat when describing Deolalikar&#039;s strategy.  Deolalikar is not quite analysing the solution spaces {x: Q(x)=1} of a problem Q that may or may not be in P.  Instead, he is considering satisfiability problems &quot;Given x, does there exist y for which R(x,y)=1?&quot; that may possibly be in P, and considering the fibres { y: R(x,y) = 1 } where x is selected in some way  from the feasible set, rather than the solution set { x: R(x,y)=1 for some y}.  Nevertheless it seems that one can modify your objection to deal with this case also, as I commented over at the other blog.]]></description>
		<content:encoded><![CDATA[<p>Over at Dick&#8217;s blog, <a HREF="http://rjlipton.wordpress.com/2010/08/12/fatal-flaws-in-deolalikars-proof/#comment-5326" rel="nofollow">Jun Tarui</a> points out that I may have oversimplified somewhat when describing Deolalikar&#8217;s strategy.  Deolalikar is not quite analysing the solution spaces {x: Q(x)=1} of a problem Q that may or may not be in P.  Instead, he is considering satisfiability problems &#8220;Given x, does there exist y for which R(x,y)=1?&#8221; that may possibly be in P, and considering the fibres { y: R(x,y) = 1 } where x is selected in some way  from the feasible set, rather than the solution set { x: R(x,y)=1 for some y}.  Nevertheless it seems that one can modify your objection to deal with this case also, as I commented over at the other blog.</p>
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		<title>By: Deolalikar&#8217;s manuscript &#171; Constraints</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8397</link>
		<dc:creator><![CDATA[Deolalikar&#8217;s manuscript &#171; Constraints]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 17:39:11 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8397</guid>
		<description><![CDATA[[...] Deolalikar&#8217;s manuscript (in a soundbite: it doesn&#8217;t work and can&#8217;t be fixed). The objection of Timothy Gowers is also worth reading. Possibly related posts: (automatically generated)P might not be equal to NP [...]]]></description>
		<content:encoded><![CDATA[<p>[...] Deolalikar&#8217;s manuscript (in a soundbite: it doesn&#8217;t work and can&#8217;t be fixed). The objection of Timothy Gowers is also worth reading. Possibly related posts: (automatically generated)P might not be equal to NP [...]</p>
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	<item>
		<title>By: Terence Tao</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8387</link>
		<dc:creator><![CDATA[Terence Tao]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 16:47:13 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8387</guid>
		<description><![CDATA[Incidentally, the model of using random reversible logic circuits to build a random polynomial length circuit reminds me of the product replacement algorithm in the theory of random walks:

http://en.wikipedia.org/wiki/Nielsen_transformation

This may only be a superficial similarity though.]]></description>
		<content:encoded><![CDATA[<p>Incidentally, the model of using random reversible logic circuits to build a random polynomial length circuit reminds me of the product replacement algorithm in the theory of random walks:</p>
<p><a href="http://en.wikipedia.org/wiki/Nielsen_transformation" rel="nofollow">http://en.wikipedia.org/wiki/Nielsen_transformation</a></p>
<p>This may only be a superficial similarity though.</p>
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	<item>
		<title>By: gowers</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8371</link>
		<dc:creator><![CDATA[gowers]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 15:23:02 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8371</guid>
		<description><![CDATA[That&#039;s a fair summary of what I think. Actually, I&#039;d say it&#039;s a bit closer than a spiritual cousin of the natural proofs barrier -- more like an illegitimate sibling. It&#039;s not rigorous, and I&#039;m not sure whether it yields any insights that are not rigorously yielded by the natural proofs, but I find the general principle, that the output of a random circuit is incredibly hard to distinguish from a random function, easier to think about than the more precise natural proofs result. Also, when you say, &quot;according to general belief,&quot; I don&#039;t actually feel that I can speak for the TCS community here. Somebody did once make an interesting comment on this blog, however, which was that Razborov believes more strongly that the output of a random circuit is pseudorandom than that factorizing is hard. (I hope I&#039;m representing the comment and Razborov&#039;s beliefs correctly.)

Another point is that it is conceivable that some very clever simplicity criterion could work, but the phrase polylog-parametrization doesn&#039;t sound sufficiently weird and contorted to feel plausible.]]></description>
		<content:encoded><![CDATA[<p>That&#8217;s a fair summary of what I think. Actually, I&#8217;d say it&#8217;s a bit closer than a spiritual cousin of the natural proofs barrier &#8212; more like an illegitimate sibling. It&#8217;s not rigorous, and I&#8217;m not sure whether it yields any insights that are not rigorously yielded by the natural proofs, but I find the general principle, that the output of a random circuit is incredibly hard to distinguish from a random function, easier to think about than the more precise natural proofs result. Also, when you say, &#8220;according to general belief,&#8221; I don&#8217;t actually feel that I can speak for the TCS community here. Somebody did once make an interesting comment on this blog, however, which was that Razborov believes more strongly that the output of a random circuit is pseudorandom than that factorizing is hard. (I hope I&#8217;m representing the comment and Razborov&#8217;s beliefs correctly.)</p>
<p>Another point is that it is conceivable that some very clever simplicity criterion could work, but the phrase polylog-parametrization doesn&#8217;t sound sufficiently weird and contorted to feel plausible.</p>
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		<title>By: Terence Tao</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8362</link>
		<dc:creator><![CDATA[Terence Tao]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 14:25:38 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8362</guid>
		<description><![CDATA[So, basically, the point is that if you get an infinite number of monkeys to design polynomial-length circuits, then the output of a typical such (or pseudorandomly selected) monkey circuit is, according to general belief, indistinguishable from that of a genuinely random function, and so it is unlikely that any sort of &quot;simplicity&quot; criterion can separate the two.   (This sounds quite close to the belief that pseudorandom number generators exist, and so perhaps this is a spiritual cousin of the natural proofs barrier after all.)

This does look to be getting at the very heart of the matter, and is quite convincing to me at least that the whole &quot;bound complexity using the structure of the solution space&quot; strategy is indeed doomed to failure.  I&#039;ll point it out on Lipton&#039;s blog.]]></description>
		<content:encoded><![CDATA[<p>So, basically, the point is that if you get an infinite number of monkeys to design polynomial-length circuits, then the output of a typical such (or pseudorandomly selected) monkey circuit is, according to general belief, indistinguishable from that of a genuinely random function, and so it is unlikely that any sort of &#8220;simplicity&#8221; criterion can separate the two.   (This sounds quite close to the belief that pseudorandom number generators exist, and so perhaps this is a spiritual cousin of the natural proofs barrier after all.)</p>
<p>This does look to be getting at the very heart of the matter, and is quite convincing to me at least that the whole &#8220;bound complexity using the structure of the solution space&#8221; strategy is indeed doomed to failure.  I&#8217;ll point it out on Lipton&#8217;s blog.</p>
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		<title>By: anonymous</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8352</link>
		<dc:creator><![CDATA[anonymous]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 13:15:23 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8352</guid>
		<description><![CDATA[A thought on defining parameters is as follows: Consider specifying a class, C, of distributions (characterized, say, by conditional independence). Suppose one would like a homeomorphism to class C from a subset of R^k; then the smallest such k would define the number of parameters required to define this class. I am not sure if it makes sense, but this is the best attempt of at least a more nuanced definition (still not complete) that I could think of while trying to capture Deolalikar&#039;s intuition.]]></description>
		<content:encoded><![CDATA[<p>A thought on defining parameters is as follows: Consider specifying a class, C, of distributions (characterized, say, by conditional independence). Suppose one would like a homeomorphism to class C from a subset of R^k; then the smallest such k would define the number of parameters required to define this class. I am not sure if it makes sense, but this is the best attempt of at least a more nuanced definition (still not complete) that I could think of while trying to capture Deolalikar&#8217;s intuition.</p>
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		<title>By: gowers</title>
		<link>http://gowers.wordpress.com/2010/08/13/could-anything-like-deolalikars-strategy-work/#comment-8339</link>
		<dc:creator><![CDATA[gowers]]></dc:creator>
		<pubDate>Fri, 13 Aug 2010 10:11:00 +0000</pubDate>
		<guid isPermaLink="false">http://gowers.wordpress.com/?p=1914#comment-8339</guid>
		<description><![CDATA[I&#039;d like to add that I&#039;ve now read the beginning of Chapter 3 of &lt;a href=&quot;http://www.hpl.hp.com/personal/Vinay_Deolalikar/Papers/pnp_8_11.pdf&quot; rel=&quot;nofollow&quot;&gt;Deolalikar&#039;s paper&lt;/a&gt; a few times. I find his definition hard to understand: I don&#039;t see precisely what it means to specify a distribution with a certain number of parameters. However, let&#039;s take a pseudorandom computable function. How could we describe its solution space efficiently? 

The distribution is certainly ample, since about half of all possible inputs belong to it. But the function mixes things up so much that it also seems to me that the various correlations amongst the n random variables (obtained if you take a random n-bit solution) will not be reducible in any sense I can think of.]]></description>
		<content:encoded><![CDATA[<p>I&#8217;d like to add that I&#8217;ve now read the beginning of Chapter 3 of <a href="http://www.hpl.hp.com/personal/Vinay_Deolalikar/Papers/pnp_8_11.pdf" rel="nofollow">Deolalikar&#8217;s paper</a> a few times. I find his definition hard to understand: I don&#8217;t see precisely what it means to specify a distribution with a certain number of parameters. However, let&#8217;s take a pseudorandom computable function. How could we describe its solution space efficiently? </p>
<p>The distribution is certainly ample, since about half of all possible inputs belong to it. But the function mixes things up so much that it also seems to me that the various correlations amongst the n random variables (obtained if you take a random n-bit solution) will not be reducible in any sense I can think of.</p>
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