arXiv research

Proves global existence for quasilinear wave equations with weak null condition.

Low-rank matrix recovery has found many applications in science and engineering such as machine learning, signal processing, collaborative filtering, system identification, and Euclidean embedding. But the low-rank matrix recovery problem is an NP hard problem and thus challenging. A commonly used heuristic approach is…

Nuclear norm minimization (NNM) has recently gained significant attention for its use in rank minimization problems. Similar to compressed sensing, using null space characterizations, recovery thresholds for NNM have been studied in \cite{arxiv,Recht_Xu_Hassibi}. However simulations show that the thresholds are far fro…

Proves inextendibility of weak null singularities from curvature blow-up.

Study proves global existence and decay for complex wave equations.

Study on unique spacetime extensions in 1+1 dimensions with applications to weak null singularities.

We study the evolution of hypersurfaces in spacetime initial data sets by their null mean curvature. A theory of weak solutions is developed using the level-set approach. Starting from an arbitrary mean convex, outer untapped hypersurface $\partialΩ_0$, we show that there exists a weak solution to the null mean curvatu…

In the Compressed Sensing community, it is well known that given a matrix $X \in \mathbb R^{n\times p}$ with $\ell_2$ normalized columns, the Restricted Isometry Property (RIP) implies the Null Space Property (NSP). It is also well known that a small Coherence $μ$ implies a weak RIP, i.e. the singular values of $X_T$ l…

Proves globally hyperbolic spacetimes via null distance completeness.

We study the nonlinear stability of the $(3+1)$-dimensional Minkowski spacetime as a solution of the Einstein vacuum equation. Similarly to our previous work on the stability of cosmological black holes, we construct the solution of the nonlinear initial value problem using an iteration scheme in which we solve a linea…

In the 60's Levine proved that if $R$ is a slice knot, then on any genus $g$ Seifert surface for $R$ there is a $g$ component link $J$, called a derivative of $R$, on which the Seifert form vanishes. Many subsequent obstructions to $R$ being slice are given in terms of slice obstructions of $J$. Many of these obstructi…

Study shows weak homotopy equivalences for complete minimal surfaces.

Totally geodesic null hypersurfaces found in Lorentzian manifolds.

Study optimal transport on null hypersurfaces and null energy condition.

The paper proves uniform Temple charts and applies them to null distance metrics.

SIMPLE-RC method tests group membership profiles in large networks with weak signals.

Identifies null hypersurfaces with constant surface gravity.

The null energy condition is characterized via convexity of entropy in Lorentzian manifolds.

The paper studies marginally trapped submanifolds in Lorentzian manifolds under null energy condition.

The study finds geometric obstructions for Einstein-Hilbert-Palatini theories.

Study constructs solutions for evolving hypersurfaces using inverse spacetime mean curvature.

The study proves a strong parametric h-principle for minimal surfaces.

In this work we obtain the limit of the Hawking energy of a large class of foliations along general null hypersurfaces $Ω$ satisfying a weak notion of asymptotic flatness. The foliations are not required to be either geodesic or approaching large spheres at infinity. The limit is obtained in terms of a reference backgr…

Synthetic framework for null hypersurfaces in non-smooth spacetimes.

We introduce a new geometric evolution equation for hypersurfaces in asymptotically flat spacetime initial data sets, that unites the theory of marginally outer trapped surfaces (MOTS) with the study of inverse mean curvature flow in asymptotically flat Riemannian manifolds. A theory of weak solutions is developed usin…

In this paper, we study inextensible flows of partially null and pseudo null curves in E_1^4. We give neccessary and sufficent conditions for inextensible flows of partially null and pseudo null curves in E_1^4

Study of mean curvature flow on null hypersurfaces leading to MOTS.

We provide the first differentially private algorithms for controlling the false discovery rate (FDR) in multiple hypothesis testing, with essentially no loss in power under certain conditions. Our general approach is to adapt a well-known variant of the Benjamini-Hochberg procedure (BHq), making each step differential…

Proves compact Cauchy horizons have constant surface gravity under null energy condition.

The main result we give in this brief note relates, under suitable hypotheses, the φ-null Osserman, the null Osserman and the classical Osserman conditions to each other, via semi-Riemannian submersions as projection maps of principal torus bundles arising from a Lorentzian S-manifold.

We clarify the relationship between the null geodesic completeness of an Einstein Lorentz manifold and its conformal Kobayashi pseudodistance. We show that an Einstein manifold has at least one incomplete null geodesic if its pseudodistancfe is nontrivial. If its pseudodistance is nondegenerate, all of its null geodesi…

The paper generalizes Alexandrov theorems for null hypersurfaces with integral curvature conditions.

Study on naked singularities without symmetry, forming incomplete future null infinity and singular inner Cauchy horizon.

Study null energy condition impacts on special hypersurfaces in static spacetimes.

The null Penrose inequality, i.e. the Penrose inequality in terms of the Bondi energy, is studied by introducing a funtional on surfaces and studying its properties along a null hypersurface $Ω$ extending to past null infinity. We prove a general Penrose-type inequality which involves the limit at infinity of the Hawki…

Unified approach to various energy conditions in spacetime geometry.

Study shows instability of naked singularities in scalar field models.

A condition of Osserman type, called $φ$-null Osserman condition, is introduced and studied in the context of Lorentz globally framed $f$-manifolds. An explicit example shows the naturalness of this condition in the setting of Lorentz $\mathcal{S}$-manifolds. We prove that a Lorentz $\mathcal{S}$-manifold with constant…

The study examines conditions that prevent null geodesic lines in spacetimes, impacting cosmological geometry.

New findings on how conformal rescalings affect spacetime metrics.

Study on convex surfaces in Minkowski space, proving completeness and incompleteness conditions.

The paper studies null hypersurfaces in 4-manifolds with a specific metric structure.

Study null hypersurfaces in Lorentzian manifolds, proving Riemannian flow structure.

Study on null helices in semi-Riemannian manifolds with special submanifolds.

We define an explicit quasi-local mass functional which is non-decreasing along all foliations (satisfying a convexity assumption) of null cones. We use this new functional to prove the null Penrose conjecture under fairly generic conditions.

In [21], the authors initiated the study of quasi generalized CR (QGCR)-null submanifolds. In this paper, attention is drawn to some distributions on ascreen QGCR-null submanifolds in an indefinite nearly cosymplectic manifold. We characterize totally umbilical and irrotational ascreen QGCR-null submanifolds. We finall…

Extends results on marginally outer trapped surfaces to general null expansion.

On a Lorentzian manifold the existence of a parallel null vector field implies certain constraint conditions on the induced Riemannian geometry of a space-like hypersurface. We will derive these constraint conditions and, conversely, show that every real analytic Riemannian manifold satisfying the constraint conditions…