All reports by Author Nutan Limaye:

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TR18-162
| 16th September 2018
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Swapnam Bajpai, Vaibhav Krishan, Deepanshu Kush, Nutan Limaye, Srikanth Srinivasan#### A #SAT Algorithm for Small Constant-Depth Circuits with PTF gates

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TR18-157
| 10th September 2018
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Nutan Limaye, Karteek Sreenivasiah, Srikanth Srinivasan, Utkarsh Tripathi, S Venkitesh#### The Coin Problem in Constant Depth: Sample Complexity and Parity gates

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TR18-135
| 31st July 2018
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Prasad Chaugule, Nutan Limaye, Aditya Varre#### Variants of Homomorphism Polynomials Complete for Algebraic Complexity Classes

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TR18-062
| 7th April 2018
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Suryajith Chillara, Christian Engels, Nutan Limaye, Srikanth Srinivasan#### A Near-Optimal Depth-Hierarchy Theorem for Small-Depth Multilinear Circuits

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TR17-156
| 15th October 2017
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Suryajith Chillara, Nutan Limaye, Srikanth Srinivasan#### Small-depth Multilinear Formula Lower Bounds for Iterated Matrix Multiplication, with Applications

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TR17-077
| 30th April 2017
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Guillaume Lagarde, Nutan Limaye, Srikanth Srinivasan#### Lower Bounds and PIT for Non-Commutative Arithmetic circuits with Restricted Parse Trees

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TR17-019
| 8th February 2017
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Andreas Krebs, Nutan Limaye, Michael Ludwig#### A Unified Method for Placing Problems in Polylogarithmic Depth

Revisions: 2

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TR16-155
| 10th October 2016
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Vaibhav Krishan, Nutan Limaye#### Isolation Lemma for Directed Reachability and NL vs. L

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TR16-143
| 15th September 2016
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Nikhil Balaji, Nutan Limaye, Srikanth Srinivasan#### An Almost Cubic Lower Bound for $\Sigma\Pi\Sigma$ Circuits Computing a Polynomial in VP

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TR15-118
| 23rd July 2015
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HervĂ© Fournier, Nutan Limaye, Meena Mahajan, Srikanth Srinivasan#### The shifted partial derivative complexity of Elementary Symmetric Polynomials

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TR15-022
| 9th February 2015
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Nutan Limaye, Guillaume Malod, Srikanth Srinivasan#### Lower bounds for non-commutative skew circuits

Revisions: 1

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TR14-183
| 25th December 2014
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Nikhil Balaji, Andreas Krebs, Nutan Limaye#### Skew Circuits of Small Width

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TR14-180
| 22nd December 2014
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Anna Gal, Jing-Tang Jang, Nutan Limaye, Meena Mahajan, Karteek Sreenivasaiah#### Space-Efficient Approximations for Subset Sum

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TR14-005
| 14th January 2014
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Neeraj Kayal, Nutan Limaye, Chandan Saha, Srikanth Srinivasan#### An Exponential Lower Bound for Homogeneous Depth Four Arithmetic Formulas

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TR13-102
| 17th July 2013
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Andreas Krebs, Nutan Limaye, Meena Mahajan, Karteek Sreenivasaiah#### Small Depth Proof Systems

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TR13-100
| 15th July 2013
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HervĂ© Fournier, Nutan Limaye, Guillaume Malod, Srikanth Srinivasan#### Lower bounds for depth $4$ formulas computing iterated matrix multiplication

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TR12-186
| 27th December 2012
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Andreas Krebs, Nutan Limaye#### DLOGTIME-Proof Systems

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TR10-103
| 28th June 2010
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Andreas Krebs, Nutan Limaye, Meena Mahajan#### Counting paths in VPA is complete for \#NC$^1$

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TR10-094
| 17th May 2010
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Ajesh Babu, Nutan Limaye, Girish Varma#### Streaming algorithms for some problems in log-space.

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TR09-052
| 2nd May 2009
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Fabian Wagner, Samir Datta, Nutan Limaye, Prajakta Nimbhorkar, Thomas Thierauf#### Planar Graph Isomorphism is in Log-space

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TR07-087
| 11th July 2007
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Nutan Limaye, Meena Mahajan, B. V. Raghavendra Rao#### Arithmetizing classes around NC^1 and L

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TR06-009
| 10th January 2006
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Nutan Limaye, Meena Mahajan, Jayalal Sarma#### Evaluating Monotone Circuits on Cylinders, Planes and Tori

Swapnam Bajpai, Vaibhav Krishan, Deepanshu Kush, Nutan Limaye, Srikanth Srinivasan

We show that there is a randomized algorithm that, when given a small constant-depth Boolean circuit $C$ made up of gates that compute constant-degree Polynomial Threshold functions or PTFs (i.e., Boolean functions that compute signs of constant-degree polynomials), counts the number of satisfying assignments to $C$ in significantly better than ... more >>>

Nutan Limaye, Karteek Sreenivasiah, Srikanth Srinivasan, Utkarsh Tripathi, S Venkitesh

The $\delta$-Coin Problem is the computational problem of distinguishing between coins that are heads with probability $(1+\delta)/2$ or $(1-\delta)/2,$ where $\delta$ is a parameter that is going to $0$. We study the complexity of this problem in the model of constant-depth Boolean circuits and prove the following results.

1. Upper ... more >>>

Prasad Chaugule, Nutan Limaye, Aditya Varre

We present polynomial families complete for the well-studied algebraic complexity classes VF, VBP, VP, and VNP. The polynomial families are based on the homomorphism polynomials studied in the recent works of Durand et al. (2014) and Mahajan et al. (2016). We consider three different variants of graph homomorphisms, namely injective ... more >>>

Suryajith Chillara, Christian Engels, Nutan Limaye, Srikanth Srinivasan

We study the size blow-up that is necessary to convert an algebraic circuit of product-depth $\Delta+1$ to one of product-depth $\Delta$ in the multilinear setting.

We show that for every positive $\Delta = \Delta(n) = o(\log n/\log \log n),$ there is an explicit multilinear polynomial $P^{(\Delta)}$ on $n$ variables that ... more >>>

Suryajith Chillara, Nutan Limaye, Srikanth Srinivasan

The complexity of Iterated Matrix Multiplication is a central theme in Computational Complexity theory, as the problem is closely related to the problem of separating various complexity classes within $\mathrm{P}$. In this paper, we study the algebraic formula complexity of multiplying $d$ many $2\times 2$ matrices, denoted $\mathrm{IMM}_{d}$, and show ... more >>>

Guillaume Lagarde, Nutan Limaye, Srikanth Srinivasan

We investigate the power of Non-commutative Arithmetic Circuits, which compute polynomials over the free non-commutative polynomial ring $\mathbb{F}\langle x_1,\dots,x_N \rangle$, where variables do not commute. We consider circuits that are restricted in the ways in which they can compute monomials: this can be seen as restricting the families of parse ... more >>>

Andreas Krebs, Nutan Limaye, Michael Ludwig

In this work we consider the term evaluation problem which involves, given a term over some algebra and a valid input to the term, computing the value of the term on that input. This is a classical problem studied under many names such as formula evaluation problem, formula value problem ... more >>>

Vaibhav Krishan, Nutan Limaye

In this work we study the problem of efficiently isolating witnesses for the complexity classes NL and LogCFL, which are two well-studied complexity classes contained in P. We prove that if there is a L/poly randomized procedure with success probability at least 2/3 for isolating an s-t path in a ... more >>>

Nikhil Balaji, Nutan Limaye, Srikanth Srinivasan

In this note, we prove that there is an explicit polynomial in VP such that any $\Sigma\Pi\Sigma$ arithmetic circuit computing it must have size at least $n^{3-o(1)}$. Up to $n^{o(1)}$ factors, this strengthens a recent result of Kayal, Saha and Tavenas (ICALP 2016) which gives a polynomial in VNP with ... more >>>

HervĂ© Fournier, Nutan Limaye, Meena Mahajan, Srikanth Srinivasan

We continue the study of the shifted partial derivative measure, introduced by Kayal (ECCC 2012), which has been used to prove many strong depth-4 circuit lower bounds starting from the work of Kayal, and that of Gupta et al. (CCC 2013).

We show a strong lower bound on the dimension ... more >>>

Nutan Limaye, Guillaume Malod, Srikanth Srinivasan

Nisan (STOC 1991) exhibited a polynomial which is computable by linear sized non-commutative circuits but requires exponential sized non-commutative algebraic branching programs. Nisan's hard polynomial is in fact computable by linear sized skew circuits (skew circuits are circuits where every multiplication gate has the property that all but one of ... more >>>

Nikhil Balaji, Andreas Krebs, Nutan Limaye

A celebrated result of Barrington (1985) proved that polynomial size, width-5 branching programs (BP) are equivalent in power to a restricted form of branching programs -- polynomial sized width-5 permutation branching programs (PBP), which in turn capture all of NC1. On the other hand it is known that width-3 PBPs ... more >>>

Anna Gal, Jing-Tang Jang, Nutan Limaye, Meena Mahajan, Karteek Sreenivasaiah

SUBSET SUM is a well known NP-complete problem:

given $t \in Z^{+}$ and a set $S$ of $m$ positive integers, output YES if and only if there is a subset $S^\prime \subseteq S$ such that the sum of all numbers in $S^\prime$ equals $t$. The problem and its search ...
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Neeraj Kayal, Nutan Limaye, Chandan Saha, Srikanth Srinivasan

We show here a $2^{\Omega(\sqrt{d} \cdot \log N)}$ size lower bound for homogeneous depth four arithmetic formulas. That is, we give

an explicit family of polynomials of degree $d$ on $N$ variables (with $N = d^3$ in our case) with $0, 1$-coefficients such that

for any representation of ...
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Andreas Krebs, Nutan Limaye, Meena Mahajan, Karteek Sreenivasaiah

A proof system for a language $L$ is a function $f$ such that Range$(f)$ is exactly $L$. In this paper, we look at proofsystems from a circuit complexity point of view and study proof systems that are computationally very restricted. The restriction we study is: they can be computed by ... more >>>

HervĂ© Fournier, Nutan Limaye, Guillaume Malod, Srikanth Srinivasan

We study the arithmetic complexity of iterated matrix multiplication. We show that any multilinear homogeneous depth $4$ arithmetic formula computing the product of $d$ generic matrices of size $n \times n$, IMM$_{n,d}$, has size $n^{\Omega(\sqrt{d})}$ as long as $d \leq n^{1/10}$. This improves the result of Nisan and Wigderson (Computational ... more >>>

Andreas Krebs, Nutan Limaye

We define DLOGTIME proof systems, DLTPS, which generalize NC0 proof systems.

It is known that functions such as Exact-k and Majority do not have NC0 proof systems. Here, we give a DLTPS for Exact-k (and therefore for Majority) and also for other natural functions such as Reach and k-Clique. Though ...
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Andreas Krebs, Nutan Limaye, Meena Mahajan

We give a \#NC$^1$ upper bound for the problem of counting accepting paths in any fixed visibly pushdown automaton. Our algorithm involves a non-trivial adaptation of the arithmetic formula evaluation algorithm of Buss, Cook, Gupta, Ramachandran (BCGR: SICOMP 21(4), 1992). We also show that the problem is \#NC$^1$ hard. Our ... more >>>

Ajesh Babu, Nutan Limaye, Girish Varma

In this paper, we give streaming algorithms for some problems which are known to be in deterministic log-space, when the number of passes made on the input is unbounded. If the input data is massive,

the conventional deterministic log-space algorithms may not run efficiently. We study the complexity of the ...
more >>>

Fabian Wagner, Samir Datta, Nutan Limaye, Prajakta Nimbhorkar, Thomas Thierauf

Graph Isomorphism is the prime example of a computational problem with a wide difference between the best known lower and upper bounds on its complexity. There is a significant gap between extant lower and upper bounds for planar graphs as well. We bridge the gap for this natural and ... more >>>

Nutan Limaye, Meena Mahajan, B. V. Raghavendra Rao

The parallel complexity class NC^1 has many equivalent models such as

polynomial size formulae and bounded width branching

programs. Caussinus et al. \cite{CMTV} considered arithmetizations of

two of these classes, #NC^1 and #BWBP. We further this study to

include arithmetization of other classes. In particular, we show that

counting paths ...
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Nutan Limaye, Meena Mahajan, Jayalal Sarma

We re-examine the complexity of evaluating monotone planar circuits

MPCVP, with special attention to circuits with cylindrical

embeddings. MPCVP is known to be in NC^3, and for the special

case of upward stratified circuits, it is known to be in

LogDCFL. We characterize cylindricality, which ...
more >>>