Title:On Weak-Space Complexity over Complex Numbers
Speaker: Raghavendra Rao B V (IIT Madras)
Details :Tue, Aug 22, 2017 4:00 PM, @ Turing Hall
 
Abstract:Two decades ago, Blum, Shub and Smale (BSS) proposed an algebraic variant of Turing Machines where tape cells can store real or complex numbers. In this talk, we give a brief overview of the BSS model of computation and complexity classes. Defining right notion of space is a challenging and an unfinished task for the BSS model of real computation. We consider the of weak-space defined by Nauraois (2007). For weak-space bounded, division-free computations over BSS machines over complex numbers with =?0 tests, we show the following: 1) The Boolean part of the weak log-space class is contained in the deterministic log-space, i.e. BP(LOGSPACE_W)subseteq DLOG. 2) There is a set Lin NC^1_C that cannot be decided by any deterministic BSS machine whose weak-space is bounded above by a polynomial in the input length, i.e., NC^1_C otsubseteq PSPACE_W. This is a joint work with Pushkar Joglekar and Siddhartha Sivakumar.