Rectified 24-cell: Difference between revisions
en>Tomruen order |
en>Tomruen |
||
Line 1: | Line 1: | ||
In the [[mathematics|mathematical]] discipline of [[graph theory]], the '''expander walk sampling theorem''' states that [[Sampling (statistics)|sampling]] [[vertex (graph theory)|vertices]] in an [[expander graph]] by doing a [[Random walk#Random walk on graphs|random walk]] is almost as good as sampling the vertices [[statistical independence|independently]] from a [[uniform distribution (discrete)|uniform distribution]]. | |||
The earliest version of this theorem is due to {{harvtxt|Ajtai|Komlós|Szemerédi|1987}}, and the more general version is typically attributed to {{harvtxt|Gillman|1998}}. | |||
==Statement== | |||
Let <math>G = (V, E)</math> be an expander graph with [[Expander graph#Spectral expansion|normalized second-largest eigenvalue]] <math>\lambda</math>. Let <math>n</math> denote the number of vertices in <math>G</math>. Let <math>f : V \rightarrow [0, 1]</math> be a function on the vertices of <math>G</math>. Let <math>\mu = E[f]</math> denote the true mean of <math>f</math>, i.e. <math>\mu = \frac{1}{n} \sum_{v \in V} f(v)</math>. Then, if we let <math>Y_0, Y_1, \ldots, Y_k</math> denote the vertices encountered in a <math>k</math>-step random walk on <math>G</math> starting at a random vertex <math>Y_0</math>, we have the following for all <math>\gamma > 0</math>: | |||
:<math>\Pr\left[\frac{1}{k} \sum_{i=0}^k f(Y_i) - \mu > \gamma\right] \leq e^{-\Omega (\gamma^2 (1-\lambda) k)}.</math> | |||
Here the <math>\Omega</math> hides an absolute constant <math>\geq 1/10</math>. An identical bound holds in the other direction: | |||
:<math>\Pr\left[\frac{1}{k} \sum_{i=0}^k f(Y_i) - \mu < -\gamma\right] \leq e^{-\Omega (\gamma^2 (1-\lambda) k)}.</math> | |||
==Uses== | |||
This theorem is useful in randomness reduction in the study of [[derandomization]]. Sampling from an expander walk is an example of a randomness-efficient [[sample (statistics)|sampler]]. Note that the number of [[bit]]s used in sampling <math>k</math> independent samples from <math>f</math> is <math>k \log n</math>, whereas if we sample from an infinite family of constant-degree expanders this costs only <math>\log n + O(k)</math>. Such families exist and are efficiently constructible, e.g. the [[Ramanujan graph]]s of [[Alexander Lubotzky|Lubotzky]]-Phillips-Sarnak. | |||
==Notes== | |||
{{reflist}} | |||
==References== | |||
{{refbegin}} | |||
* {{citation | |||
| first1=M. | last1=Ajtai | |||
| first2=J. | last2=Komlós | |||
| first3=E. | last3=Szemerédi | |||
| title=Deterministic simulation in LOGSPACE | |||
| booktitle=Proceedings of the nineteenth annual ACM symposium on Theory of computing | |||
| pages=132–140 | |||
| year=1987 | |||
| work=ACM | |||
| doi=10.1145/28395.28410 | |||
}} | |||
* {{citation | |||
| first=D. | last=Gillman | |||
| title=A Chernoff Bound for Random Walks on Expander Graphs | |||
| journal=SIAM Journal on Computing | |||
| volume=27 | |||
| pages=1203–1220 | |||
| year=1998 | |||
| publisher=Society for Industrial and Applied Mathematics | |||
| doi=10.1137/S0097539794268765 | |||
| issue=4, | |||
}} | |||
{{refend}} | |||
==External links== | |||
* Proofs of the expander walk sampling theorem. [http://citeseer.ist.psu.edu/gillman98chernoff.html] [http://projecteuclid.org/Dienst/UI/1.0/Summarize/euclid.aoap/1028903453] | |||
[[Category:Sampling (statistics)]] |
Revision as of 06:53, 22 November 2013
In the mathematical discipline of graph theory, the expander walk sampling theorem states that sampling vertices in an expander graph by doing a random walk is almost as good as sampling the vertices independently from a uniform distribution. The earliest version of this theorem is due to Template:Harvtxt, and the more general version is typically attributed to Template:Harvtxt.
Statement
Let be an expander graph with normalized second-largest eigenvalue . Let denote the number of vertices in . Let be a function on the vertices of . Let denote the true mean of , i.e. . Then, if we let denote the vertices encountered in a -step random walk on starting at a random vertex , we have the following for all :
Here the hides an absolute constant . An identical bound holds in the other direction:
Uses
This theorem is useful in randomness reduction in the study of derandomization. Sampling from an expander walk is an example of a randomness-efficient sampler. Note that the number of bits used in sampling independent samples from is , whereas if we sample from an infinite family of constant-degree expanders this costs only . Such families exist and are efficiently constructible, e.g. the Ramanujan graphs of Lubotzky-Phillips-Sarnak.
Notes
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
References
- Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.
Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.
Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.
To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010 - Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.
Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.
In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.
Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region
Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.
15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.
To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010