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Paper Abstract and Keywords
Presentation 2020-09-02 11:30
What Restrictions Naturally Allow Well-Known NP-Complete Problems to Yield NL-Completeness and the Linear Space Hypothesis?
Tomoyuki Yamakami (U of Fukui) COMP2020-10
Abstract (in Japanese) (See Japanese page) 
(in English) Many practical combinatorial problems have been shown to be NP-complete or NP-hard. To cope with further real-life situations of those problems, we are often focused on their subproblems obtained naturally by imposing reasonable restrictions onto their instances or their key properties. Those subproblems in general turn out to have much lower complexity than the original problems do.
We are interested in what types of restrictions significantly affect the computational complexities of most well-known NP-complete problems. In particular, we seek natural restrictions that force various NP-complete problems to become NL-complete. With further restrictions, we may make their parameterizations equivalent to a practical working hypothesis, known as the linear space hypothesis (LSH), which is related to the space complexity upper bound of a weak form of the parameterized 2SAT. As a direct consequence, under the assumption of LSH, we obtain sub-linear lower bounds on the space complexity necessary to solve various NL-complete problems within polynomially many steps.
Keyword (in Japanese) (See Japanese page) 
(in English) parameterized decision problem / linear space hypothesis / NP-complete problem / NL-complete problem / nondeterministic logarithmic space / / /  
Reference Info. IEICE Tech. Rep., vol. 120, no. 152, COMP2020-10, pp. 33-40, Sept. 2020.
Paper # COMP2020-10 
Date of Issue 2020-08-25 (COMP) 
ISSN Online edition: ISSN 2432-6380
All rights are reserved and no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Notwithstanding, instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. (License No.: 10GA0019/12GB0052/13GB0056/17GB0034/18GB0034)
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Conference Information
Committee COMP IPSJ-AL  
Conference Date 2020-09-01 - 2020-09-02 
Place (in Japanese) (See Japanese page) 
Place (in English) Online 
Topics (in Japanese) (See Japanese page) 
Topics (in English)  
Paper Information
Registration To COMP 
Conference Code 2020-09-COMP-AL 
Language English 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) What Restrictions Naturally Allow Well-Known NP-Complete Problems to Yield NL-Completeness and the Linear Space Hypothesis? 
Sub Title (in English)  
Keyword(1) parameterized decision problem  
Keyword(2) linear space hypothesis  
Keyword(3) NP-complete problem  
Keyword(4) NL-complete problem  
Keyword(5) nondeterministic logarithmic space  
1st Author's Name Tomoyuki Yamakami  
1st Author's Affiliation University of Fukui (U of Fukui)
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Speaker Author-1 
Date Time 2020-09-02 11:30:00 
Presentation Time 30 minutes 
Registration for COMP 
Paper # COMP2020-10 
Volume (vol) vol.120 
Number (no) no.152 
Page pp.33-40 
Date of Issue 2020-08-25 (COMP) 

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