Error-correcting codes are a method for representing data, so that one can recover the original information even if some parts of it were corrupted. The basic idea, which dates back to the revolutionary work of Shannon and Hamming about a century ago, is to encode the data into a ... more >>>

In this work, we establish the first separation between computation with bounded and unbounded space, for problems with short outputs (i.e., working memory can be exponentially larger than output size), both in the classical and the quantum setting. Towards that, we introduce a problem called nested collision finding, and show ... more >>>

We introduce spiky rank, a new matrix parameter that enhances blocky rank by combining the combinatorial structure of the latter with linear-algebraic flexibility. A spiky matrix is block-structured with diagonal blocks that are arbitrary rank-one matrices, and the spiky rank of a matrix is the minimum number of such matrices ... more >>>

We study deterministic polynomial identity testing (PIT) and reconstruction algorithms for depth-$4$ arithmetic circuits of the form
\[
\Sigma^{[r]}\!\wedge^{[d]}\!\Sigma^{[s]}\!\Pi^{[\delta]}.
\]
This model generalizes Waring decompositions and diagonal circuits, and captures sums of powers of low-degree sparse polynomials. Specifically, each circuit computes a sum of $r$ terms, where each term is ... more >>>

We study the implications of the existence of weak Zero-Knowledge (ZK) protocols for worst-case hard languages. These are protocols that have completeness, soundness, and zero-knowledge errors (denoted $\epsilon_c$, $\epsilon_s$, and $\epsilon_z$, respectively) that might not be negligible. Under the assumption that there are worst-case hard languages in NP, we show ... more >>>

We present efficient quantum circuits that implement high-dimensional unitary irreducible representations (irreps) of SU(n), where n>=2 is constant. For dimension N and error ?, the number of quantum gates in our circuits is polynomial in log(N) and log(1/?). Our construction relies on the Jordan-Schwinger representation, which allows us to realize ... more >>>

Guo, Saxena, and Sinhababu (TOC'18, CCC'18) defined a natural, approximative analog of the polynomial system satisfiability problem, which they called approximate polynomial satisfiability (APS). They proved algebraic and geometric properties of it and showed an NP-hardness lower bound and a PSPACE upper bound for it. They further established how the ... more >>>

The complexity of bilinear maps (equivalently, of $3$-mode tensors) has been studied extensively, most notably in the context of matrix multiplication. While circuit complexity and tensor rank coincide asymptotically for $3$-mode tensors, this correspondence breaks down for $d \geq 4$ modes. As a result, the complexity of $d$-mode tensors for ... more >>>

We show that Hilbert's Nullstellensatz, the problem of deciding if a system of multivariate polynomial equations has a solution in the algebraic closure of the underlying field, lies in the counting hierarchy. More generally, we show that the number of solutions to a system of equations can be computed in ... more >>>

Unlike in TFNP, for which there is an abundance of problems capturing natural existence principles which are incomparable (in the black-box setting), Kleinberg et al. [KKMP21] observed that many of the natural problems considered so far in the second level of the total function polynomial hierarchy (TF$\Sigma_2$) reduce to the ... more >>>

We give new algorithms for tree evaluation (S. Cook et. al. TOCT 2012) in the catalytic-computing model (Buhrman et. al. STOC 2014). Two existing approaches aim to solve tree evaluation in low space: on the one hand, J. Cook and Mertz (STOC 2024) give an algorithm for TreeEval running in ... more >>>

Symmetry of Information (SoI) is a fundamental result in Kolmogorov complexity stating that for all $n$-bit strings $x$ and $y$, $K(x,y) = K(y) + K(x \mid y)$ up to an additive error of $O(\log n)$ [ZL70]. In contrast, understanding whether SoI holds for time-bounded Kolmogorov complexity measures is closely related ... more >>>

We show an unconditional classical oracle separation between the class of languages that can be verified using a quantum proof (QMA) and the class of languages that can be verified with a classical proof (QCMA). Compared to the recent work of Bostanci, Haferkamp, Nirkhe, and Zhandry (STOC 2026), our proof ... more >>>

We prove that for any 3-player game $\mathcal G$, whose query distribution has the same support as the GHZ game (i.e., all $x,y,z\in \{0,1\}$ satisfying $x+y+z=0\pmod{2}$), the value of the $n$-fold parallel repetition of $\mathcal G$ decays exponentially fast: \[ \text{val}(\mathcal G^{\otimes n}) \leq \exp(-n^c)\] for all sufficiently large $n$, ... more >>>

We show that for any unsatisfiable CNF formula $\varphi$ that requires resolution refutation width at least $w$, and for any $1$-stifling gadget $g$ (for example, $g=MAJ_3$), (1) every resolution-over-parities (Res($\oplus$)) refutation of the lifted formula $\varphi \circ g$ of size at most $S$ has depth at least $\Omega(w^2/\log S)$; (2) ... more >>>

The hardness vs. randomness paradigm aims to construct pseudorandom generators (PRGs) based on complexity theoretic hardness assumptions. A seminal result in this area is a PRG construction by \cite{NW,IW97}.
A sequence of works \cite{KvM,SU01,Umans02,SU05} generalized the result of \cite{NW,IW97} to nondeterministic circuits. More specifically, they showed that if $\E=\DTIME(2^{O(n)})$ requires ... more >>>

Pseudorandom generators (PRGs) for low-degree polynomials are a central object in pseudorandomness, with applications to circuit lower bounds and derandomization. Viola’s celebrated construction (CC 2009) gives a PRG over the binary field, but with seed length exponential in the degree $d$. This exponential dependence can be avoided over sufficiently large ... more >>>

In this work, we propose a new bounded arithmetic theory, denoted $\mathbf{APX}_1$, designed to formalize a broad class of probabilistic arguments commonly used in theoretical computer science. Under plausible assumptions, $\mathbf{APX}_1$ is strictly weaker than previously proposed frameworks, such as the theory $\mathbf{APC}_1$ introduced in the seminal work of Je?ábek ... more >>>

We prove a switching lemma for constant-depth circuits over the alphabet $F_p$ with generalized AND/OR gates, extending Tal's Fourier-analytic approach from the Boolean setting. The key new ingredient is a direct computation of the $L_1$ Fourier mass of AND/OR gates over $F_p$, which yields an exact closed-form expression for the ... more >>>

A major open problem at the interface of quantum computing and communication complexity is whether quantum protocols can be exponentially more efficient than classical protocols for computing total Boolean functions; the prevailing conjecture is that they are not. In a seminal work, Razborov (2002) resolved this question for AND-functions of ... more >>>

We study systems of linear equations modulo two in $n$ variables
with three variables in each equation. We assume that the system has
a solution with $pn$ variables taking the value 1 for some value
$00$ it is hard to find a solution
of the same weight that satisfies at ... more >>>

We introduce the SHEDAG (Somewhere Honest Entropic sources over Directed Acyclic Graphs) source model, a general model for multi-block randomness sources with causal correlations.
A SHEDAG source is defined over a directed acyclic graph (DAG) $G$ whose nodes output $n$-bit blocks. Blocks output by honest nodes are independent (by ... more >>>

This paper explores the previously studied measure called block number of Boolean functions, that counts the maximum possible number of minimal sensitive blocks for any input. We present close to tight upper bounds on the block number in terms of the function’s sensitivity and the allowed block size, improving previous ... more >>>

In this short expository note, we provide an introduction to a distribution testing (and, more generally, indistinguishability) lower bound method based on moment-matching via polynomials. This method, which underlies several of the tight lower bounds on estimating symmetric properties, had for many years appeared mysterious and near-magical to the ... more >>>

Proving super-linear lower bounds on the size of circuits computing explicit linear functions $A:{\mathbb {F}}^n \to {\mathbb {F}}^n$ is a fundamental long-standing open problem in circuit complexity. We focus on the case where ${\mathbb {F}}$ is a finite field. The circuit can be either a Boolean circuit or an arithmetic ... more >>>

Res($\oplus$) is the simplest fragment of $\text{AC}^0[2]\text{-Frege}$ for which no super-polynomial lower bounds on the size of proofs are known. Bhattacharya and Chattopadhyay [BC25] recently proved lower bounds of the form $\exp(\tilde\Omega(N^{\varepsilon}))$ on the size of Res($\oplus$) proofs whose depth is upper bounded by $O(N^{2 - \varepsilon})$, where $N$ is ... more >>>

We prove that relative to a random oracle answering $O(\log n)$-bit queries, there exists a function computable in $O(n)$ time by a random-access machine (RAM) but requiring $n^2/polylog(n)$ time by any multitape Turing machine. This provides strong evidence that simulating RAMs on multitape Turing machines inherently incurs a nearly quadratic ... more >>>

We prove that $\mathrm{deg}(f) \leq 2 \, \mathrm{rdeg}(f)^4$ for every Boolean function $f$, where $\mathrm{deg}(f)$ is the degree of $f$ and $\mathrm{rdeg}(f)$ is the rational degree of $f$. This resolves the second of the three open problems stated by Nisan and Szegedy, and attributed to Fortnow, in 1994.

We present a new, simplified proof that the complexity class BPP is contained in the Polynomial Hierarchy (PH), using $k$-wise independent hashing as the main tool. We further extend this approach to recover several other previously known inclusions between complexity classes. Our techniques are inspired by the work of Bellare, ... more >>>

Let $g(X)$ be a polynomial over a finite field ${\mathbb F}_q$ with degree $o(q^{1/2})$, and let $\chi$ be the quadratic residue character. We give a polynomial time algorithm to recover $g(X)$ (up to perfect square factors) given the values of $\chi \circ g$ on ${\mathbb F}_q$, with up to a ... more >>>

In this work, we establish separation theorems for several subsystems of the Ideal Proof System (IPS), an algebraic proof system introduced by Grochow and Pitassi (J. ACM, 2018). Separation theorems are well-studied in the context of classical complexity theory, Boolean circuit complexity, and algebraic complexity.

In an important work ... more >>>

It is a long-standing open problem in algebraic complexity to prove lower bounds against multilinear algebraic branching programs (mABPs). The best lower bounds in this setting are still quadratic (Alon, Kumar and Volk (Combinatorica 2020)). At the same time, it remains a possibility that the “min-partition rank” method introduced by ... more >>>