José Madrid

activity

20142026

most citedDerivative bounds for fractional maximal functions

83 citations · 156 across the 27 of their papers we have counts for

collaborators

37 papers

math.CA2026

On $L^{p}$ norms of maximal operators

Valentina Ciccone, Mahdi Hormozi, José Madrid +2

We study the exact $L^{p}$ norms for a number of maximal operators, which are prominent in harmonic analysis, semigroup theory, and probability. We prove that a strongly continuous p…

math.CA2026

Sharp endpoint extension inequalities for the moment curve on finite fields II: an extremal property of the uniform distribution

Chandan Biswas, Emanuel Carneiro, Taryn C. Flock +4

We identify the optimal constant and describe all maximizers for the Fourier endpoint extension inequality associated with the moment curve over finite fields. This confirms a conj…

math.CA2026

The norm of the centered Hardy--Littlewood maximal operator

José Madrid

We determine the exact $L^{p} (R)$ norm of the centered Hardy--Littlewood maximal operator for every $1 < p < \infty$ , proving that it equals $p / (p - 1)$ . This settles the sharp st…

math.GR2026

Internal numerical semigroups

Mario Casas, José A. Madrid, J. C. Rosales

In this paper the tree structure of numerical semigroups is studied. An internal numerical semigroup is a semigroup located in an internal node of the tree. Analogous a leaf numeri…

math.PR2026

Convex order, log-convexity and moments of averages of random variables

Felipe Gonçalves, José Madrid, Antonio Pedro Ramos

We establish a convex order comparison for products of averages of exchangeable nonnegative random variables. As a consequence, we solve a conjecture of Lamkin and Tkocz (2022) on…

math.CA2026

Sharp higher order regularity of discrete maximal functions

Sung-Yi Liao, José Madrid, Eyvindur Palsson +1

We derive sharp $ℓ^{p} (Z)$ bounds for the $k$ th derivative of the discrete uncentered maximal operator applied to characteristic functions $f : Z \to {0, 1}$ in the…

math.FA2026

Carbery's inequality in the Schatten--von Neumann classes

Ziang Chen, Paata Ivanisvili, Jose Madrid +1

Carbery posed a question of sharpened triangle inequalities for families of operators in the Schatten--von Neumann classes $S_{p}$ , $p \geq 2$ . He established a weaker form of the des…

math.CA2026

Almost-Orthogonality in Lp Spaces: A Case Study with Grok

Ziang Chen, Jaume de Dios Pont, Paata Ivanisvili +2

Carbery proposed the following sharpened form of triangle inequality for many functions: for any $p \geq 2$ and any finite sequence $(f_{j})_{j} \subset L^{p}$ we have \[ \Big\|\sum_j f_j\B…

math.CA2026

The smoothest average and some extremal problems for polynomials

José Gaitán, Carlos Garzón, José Madrid

We study the problem of finding the "smoothest'' local average of a function $f \in ℓ^{2} (Z)$ when we consider its convolution with suitable kernels $u$ . The measurement…

math.CA2026

Sharp variational inequalities for the Hardy-Littlewood maximal operator on finite undirected graphs

Cristian González-Riquelme, Vjekoslav Kovač, José Madrid

We study sharp $p$ -variational inequalities for the Hardy-Littlewood maximal operator on complete graphs, answering in the affirmative a question by Feng Liu and Qingying Xue. We a…

math.CA2025

On suprema of convolutions on discrete cubes

José Gaitan, José Madrid

We find the optimal constant $C$ such that \begin{equation*} \|f_1*f_2*\dots*f_{k}\|_{\infty}\geq C\prod_{i=1}^{k}\|f_i\|_1 \end{equation*} for functions $f_i:\{0,1\}^d\to\mathbb{R…

math.CO2023★ 4 cited

Positive and Negative Square Energies of Graphs

Aida Abiad, Leonardo de Lima, Dheer Noal Desai +3

The energy of a graph $G$ is the sum of the absolute values of the eigenvalues of the adjacency matrix of $G$ . Let $s^{+} (G), s^{-} (G)$ denote the sum of the squares of the positive an…

math.CA2023★ 1 cited

On sharp isoperimetric inequalities on the hypercube

David Beltran, Paata Ivanisvili, José Madrid

We prove the sharp isoperimetric inequality $E h_{A}^{l o g_{2} (3/2)} \geq μ (A)^{*} (lo g_{2} (1/ μ (A)^{*}))^{l o g_{2} (3/2)}$ for all sets $A \subseteq {0, 1}^{n}$ , wher…

math.CA2023

Mixed norm $l^{2}$ decoupling for paraboloids

Shival Dasu, Hongki Jung, Zane Kun Li +1

We prove the sharp mixed norm $(l^{2}, L_{t}^{q} L_{x}^{r})$ decoupling estimate for the paraboloid in $d + 1$ dimensions.

math-ph2022

Comparison of Ising Models Under Change of Apriori Measure

José Madrid, Barry Simon, Daniel R. Wells

We study comparison of correlation functions for ferromagnetic generalized Ising models with two different apriori measures. One purpose of this note is to publicize some unpublish…

math.PR2022★ 1 cited

A new proof of the description of the convex hull of space curves with totally positive torsion

Jaume de Dios Pont, Paata Ivanisvili, José Madrid

We give new proofs of the description convex hulls of space curves $γ : [a, b] \mapsto R^{d}$ having totally positive torsion. These are curves such that all the leading pri…

math.CO2021★ 1 cited

Additive energies on discrete cubes

Jaume de Dios Pont, Rachel Greenfeld, Paata Ivanisvili +1

We prove that for $d \geq 0$ and $k \geq 2$ , for any subset $A$ of a discrete cube ${0, 1}^{d}$ , the $k -$ higher energy of $A$ (the number of $2 k -$ tuples $(a_{1}, a_{2}, \dots, a_{2 k})$ in $A…

math.DS2021★ 1 cited

Generalized Collatz Maps with Almost Bounded Orbits

Felipe Gonçalves, Rachel Greenfeld, Jose Madrid

If dividing by $p$ is a mistake, multiply by $q$ and translate, and so you'll live to iterate. We show that if we define a Collatz-like map in this form then, under suitable condit…

math.CA2021

On classical inequalities for autocorrelations and autoconvolutions

Jaume de Dios Pont, José Madrid

In this paper we study an autocorrelation inequality proposed by Barnard and Steinerberger. The study of these problems is motivated by a classical problem in additive combinatoric…

math.CA2021

Continuity of the gradient of the fractional maximal operator on $W^{1, 1} (R^{d})$

David Beltran, Cristian González-Riquelme, José Madrid +1

We establish that the map $f \mapsto ∣\nabla M_{α} f ∣$ is continuous from $W^{1, 1} (R^{d})$ to $L^{q} (R^{d})$ , where $α \in (0, d)$ , $q = \frac{d}{d - α}$ and $\mathca…

math.DS2021

An uncountable ergodic Roth theorem and applications

Polona Durcik, Rachel Greenfeld, Annina Iseli +2

We establish an uncountable amenable ergodic Roth theorem, in which the acting group is not assumed to be countable and the space need not be separable. This generalizes a previous…

math.CA2020★ 1 cited

Decoupling for fractal subsets of the parabola

Alan Chang, Jaume de Dios Pont, Rachel Greenfeld +3

We consider decoupling for a fractal subset of the parabola. We reduce studying $l^{2} L^{p}$ decoupling for a fractal subset on the parabola ${(t, t^{2}) : 0 \leq t \leq 1}$ to stu…

math.CA2020

Sharp inequalities for maximal operators on finite graphs, II

Cristian González-Riquelme, José Madrid

Let $M_{G}$ be the centered Hardy-Littlewood maximal operator on a finite graph $G$ . We find $p \to \infty lim ∥ M_{G} ∥_{p}^{p}$ when $G$ is the start graph ( $S_{n}$ ) an…

math.CA2020

Sunrise strategy for the continuity of maximal operators

Emanuel Carneiro, Cristian González-Riquelme, José Madrid

In this paper we address the $W^{1, 1}$ -continuity of several maximal operators at the gradient level. A key idea in our global strategy is the decomposition of a maximal operator,…

On Lp norms of maximal operators

Sharp endpoint extension inequalities for the moment curve on finite fields II: an extremal property of the uniform distribution

The norm of the centered Hardy--Littlewood maximal operator

Internal numerical semigroups

Convex order, log-convexity and moments of averages of random variables

Sharp higher order regularity of discrete maximal functions

Carbery's inequality in the Schatten--von Neumann classes

Almost-Orthogonality in Lp Spaces: A Case Study with Grok

The smoothest average and some extremal problems for polynomials

Sharp variational inequalities for the Hardy-Littlewood maximal operator on finite undirected graphs

On suprema of convolutions on discrete cubes

Positive and Negative Square Energies of Graphs

On sharp isoperimetric inequalities on the hypercube

Mixed norm l2 decoupling for paraboloids

Comparison of Ising Models Under Change of Apriori Measure

A new proof of the description of the convex hull of space curves with totally positive torsion

Additive energies on discrete cubes

Generalized Collatz Maps with Almost Bounded Orbits

On classical inequalities for autocorrelations and autoconvolutions

Continuity of the gradient of the fractional maximal operator on W1,1(Rd)

An uncountable ergodic Roth theorem and applications

Decoupling for fractal subsets of the parabola

Sharp inequalities for maximal operators on finite graphs, II

Sunrise strategy for the continuity of maximal operators

On $L^{p}$ norms of maximal operators

Mixed norm $l^{2}$ decoupling for paraboloids

Continuity of the gradient of the fractional maximal operator on $W^{1, 1} (R^{d})$