Negative / Null Result ReportOpen accessMathematics
Michel Duprez, Pierre Lissy · 2017 · arXiv
This paper is devoted to studying the null and approximate controllability of two linear coupled parabolic equations posed on a smooth domain of R^N (N>1) with coupling terms of zero and first orders and one control localized in some arbitrary nonempty open subset of the domain. We prove the null controllability under a new sufficient condition and we also provide the first example of a not approximately controllable system in the case where the support of one of the nontrivial first order coupling terms intersects the control domain.
Negative / Null Result ReportOpen accessComputer Science
Tourjana Islam Supti, Israa Abuelezz, Aya Muhanad et al. · 2025 · arXiv
This study investigates the efficacy of role-taking and literacy-based interventions in reducing the influence of appearance cues, such as gender, age, ethnicity, and clothing style, on trust and risk-taking in social engineering contexts. A-4 (Group: Control, Literacy, Persuader, Persuadee) * 2 (Time: Pre, Post) mixed factorial design was implemented over two weeks with 139 participants. The control group received no material. The literacy group attended two sessions focused on how behavior can be similar regardless of appearance cues. The persuader group completed three sessions, learning ho
Negative / Null Result ReportOpen accessComputer Science
E. V. Arbuzova · 2024 · arXiv
The search for supersymmetric partners at Large Hadron Collider revealed negative result. Though, strictly speaking, it does not exclude low energy supersymmetry, but still it leads to strong constraints of the parameter space. Therefore the search for supersymmetric particles at higher energies becomes of interest. It is shown that in $R^2$-modified cosmology heavy particles with the interaction strength typical for supersymmetry could be promising candidates for carriers of dark matter. We consider the heating of the Universe at the post-inflationary stage via particle production by oscillat
Negative / Null Result ReportOpen accessComputer Science
T. Maeno, M. Fujikawa, J. Kataoka et al. · 1995 · arXiv
We have searched for an exotic decay of orthopositronium into a single photon and a short-lived neutral boson in the hitherto unexplored mass region above 900 ${\rm keV}/{\it c}^{2}$, by noting that this decay is one of few remaining candidates which could explain the discrepancy of the orthopositronium decay-rate. A high-resolution measurement of the associated photon energy spectrum was carried out with a germanium detector to search for a sharp peak from this two-body decay. Our negative result provides the upper-limits of\mbox{ }$2.0 \times 10^{-4}$ on the branching ratio of such a decay i
Negative / Null Result ReportOpen accessMathematics
Kevin Barreto, Jiwon Kang, Sang-hyun Kim et al. · 2026 · arXiv
Answering a question of Erdős and Graham, we show that the double exponential growth condition $\limsup_{n\to\infty}a_n^{1/φ^n}=\infty$ for a strictly increasing sequence of positive integers $\{a_n\}_{n=1}^\infty$ is sufficient for the series $\sum_{n=1}^\infty 1/(a_n a_{n+1})$ to have an irrational sum; here $φ$ denotes the golden ratio. We also provide a positive generalization to $\sum_{n=1}^\infty 1/(a_n^{w_0}\cdots a_{n+d-1}^{w_{d-1}})$, and a negative result showing that some of its instances are essentially optimal. The original problem was autonomously solved by the AI agent \emph{Ale
Failed Experiment ReportOpen accessAgricultural and Biological Sciences
M. Khasin, M. I. Dykman, B. Meerson · 2009 · arXiv
We consider optimal vaccination protocol where the vaccine is in short supply. In this case, disease extinction results from a large and rare fluctuation. We show that the probability of such fluctuation can be exponentially increased by vaccination. For periodic vaccination with fixed average rate, the optimal vaccination protocol is model independent and presents a sequence of short pulses. The effect of vaccination can be resonantly enhanced if the pulse period coincides with the characteristic period of the disease dynamics or its multiples. This resonant effect is illustrated using a simp
Negative / Null Result ReportOpen accessComputer Science
Andrew Fish, Alexei Lisitsa · 2014 · arXiv
We explore the application of automated reasoning techniques to unknot detection, a classical problem of computational topology. We adopt a two-pronged experimental approach, using a theorem prover to try to establish a positive result (i.e. that a knot is the unknot), whilst simultaneously using a model finder to try to establish a negative result (i.e. that the knot is not the unknot). The theorem proving approach utilises equational reasoning, whilst the model finder searches for a minimal size counter-model. We present and compare experimental data using the involutary quandle of the knot,
Negative / Null Result ReportOpen accessComputer Science
A. Rubbia, P. Sala · 2002 · arXiv
The possibility to improve the CERN to Gran Sasso neutrino beam performances for theta_{13} searches is investigated. We show that by an appropriate optimization of the target and focusing optics of the present CNGS design, we can increase the flux of low energy neutrinos by about a factor 5 compared to the current tau optimized focalisation. With the ICARUS 2.35 kton detector at LNGS and in case of negative result, this would allow to improve the limit to sin^22 theta_{13} by an order of magnitude better than the current limit of CHOOZ at Delta m^2 approximately 3 times 10^{-3} eV^2 within 5
Negative / Null Result ReportOpen accessComputer Science
Aarón Villanueva, Peyman Najafi, Hilbert J. Kappen · 2022 · arXiv
We study quantum annealing for combinatorial optimization with Hamiltonian $H = z H_f + H_0$ where $H_f$ is diagonal, $H_0=-|φ\rangle \langle φ|$ is the equal superposition state projector and $z$ the annealing parameter. We analytically compute the minimal spectral gap as $\mathcal{O}(1/\sqrt{N})$ with $N$ the total number of states and its location $z_*$. We show that quantum speed-up requires an annealing schedule which demands a precise knowledge of $z_*$, which can be computed only if the density of states of the optimization problem is known. However, in general the density of states is
Negative / Null Result ReportOpen accessMathematics
Itai Benjamini, Alexander Shamov, Barak Weiss · 2026 · arXiv
We present an open problem about non-colliding freely moving hard disks in the Euclidean plane, together with related positive and negative partial results. The open problem is stated in a non-degenerate form: velocities are required to be pairwise distinct and their speeds are required to be uniformly bounded away from infinity. The positive deterministic result gives a bounded, injective, non-colliding velocity assignment for the integer lattice; after a common velocity shift, the speeds are also bounded away from zero. The negative result shows that no bounded continuous vector field on the
Negative / Null Result ReportOpen accessComputer Science
Michał Pilipczuk · 2011 · arXiv
We introduce a variant of modal logic, dubbed EXISTENTIAL COUNTING MODAL LOGIC (ECML), which captures a vast majority of problems known to be tractable in single exponential time when parameterized by treewidth. It appears that all these results can be subsumed by the theorem that model checking of ECML admits an algorithm with such complexity. We extend ECML by adding connectivity requirements and, using the Cut&Count technique introduced by Cygan et al. [4], prove that problems expressible in the extension are also tractable in single exponential time when parameterized by treewidth; however
Negative / Null Result ReportOpen accessComputer Science
Ramon Lapiedra, Juan Antonio Morales-Lladosa · 2013 · arXiv
Recently, some Lema{î}tre-Tolman-Bondi metrics have been considered as models alternative to the dark energy within the Friedmann-Lema{î}tre-Robertson-Walker universes. The vanishing of the intrinsic energy of these metrics is examined since such a vanishing, in the present case and in general, could be interpreted as a necessary condition to consider the possibility of the quantum creation of a metric. More specifically, this vanishing is examined in the particular case where the Lema{î}tre-Tolman-Bondi metrics behave asymptotically like a Friedmann-Lema{î}tre-Robertson-Walker universe. Final
Negative / Null Result ReportOpen accessPhysics
M. B. Bell, S. P. Comeau · 2003 · arXiv
The high number of QSOs around NGC 6212 allows a correlation analysis to be carried out between their redshift distribution and the redshift distributions predicted by intrinsic redshift models. We find no correlation between the QSO redshift distribution and the intrinsic redshifts predicted by Karlsson's log(1+z) = 0.089 relation. However, we find that the QSO redshift distribution is correlated with the intrinsic redshifts predicted by the relation z_{iQ} = 0.62[N-0.1M_{N}], for N = 3. We also find evidence that the observed redshifts of the QSOs contain a small cosmological redshift compon
Negative / Null Result ReportOpen accessComputer Science
Adrien Boiret, Radosław Piórkowski, Janusz Schmude · 2018 · arXiv
In the past decades, classical results from algebra, including Hilbert's Basis Theorem, had various applications in formal languages, including a proof of the Ehrenfeucht Conjecture, decidability of HDT0L sequence equivalence, and decidability of the equivalence problem for functional tree-to-string transducers. In this paper, we study the scope of the algebraic methods mentioned above, particularily as applied to the equivalence problem for register automata. We provide two results, one positive, one negative. The positive result is that equivalence is decidable for MSO transformations on uno
Negative / Null Result ReportOpen accessMedicine
Amate A, Lieberman M · 2026 · Harm reduction journal
Medetomidine has recently emerged in the illicit drug supply in the United States, and lateral flow immunoassay test strips are an inexpensive and easy-to-use field screening option for detecting this highly potent sedative. However, the…
View details →DOI: 10.1186/s12954-025-01387-6 Negative / Null Result ReportOpen accessComputer Science
Lukas Graf, Tobias Harks, Julian Schwarz · 2025 · arXiv
A seminal result of [Fleischer et al. and Karakostas and Kolliopulos, both FOCS 2004] states that system optimal multi-commodity static network flows are always implementable as tolled Wardrop equilibrium flows even if users have heterogeneous value-of-time sensitivities. Their proof uses LP-duality to characterize the general implementability of network flows by tolls. For the much more complex setting of $\textit{dynamic flows}$, [Graf et al., SODA 2025] identified necessary and sufficient conditions for a dynamic $s$-$d$ flow to be implementable as a tolled dynamic equilibrium. They used th
Negative / Null Result ReportOpen accessMathematics
Han Huang · 2016 · arXiv
It is natural to ask whether the center of mass of a convex body $K\subset \mathbb{R}^n$ lies in its John ellipsoid $B_K$, i.e., in the maximal volume ellipsoid contained in $K$. This question is relevant to the efficiency of many algorithms for convex bodies. In this paper, we obtain an unexpected negative result. There exists a convex body $K\subset \mathbb{R}^n$ such that its center of mass does not lie in the John ellipsoid $B_K$ inflated $(1-C\sqrt{\frac{\log(n)} {n}})n$ times about the center of $B_K$. Moreover, there exists a polytope $P \subset \mathbb{R}^n$ with $O(n^2)$ facets whose
Negative / Null Result ReportOpen accessMathematics
Petra Laketa, Stanislav Nagy · 2022 · arXiv
The halfspace depth of a $d$-dimensional point $x$ with respect to a finite (or probability) Borel measure $μ$ in $\mathbb{R}^d$ is defined as the infimum of the $μ$-masses of all closed halfspaces containing $x$. A natural question is whether the halfspace depth, as a function of $x \in \mathbb{R}^d$, determines the measure $μ$ completely. In general, it turns out that this is not the case, and it is possible for two different measures to have the same halfspace depth function everywhere in $\mathbb{R}^d$. In this paper we show that despite this negative result, one can still obtain a substan
Negative / Null Result ReportOpen accessComputer Science
Calvin McCarter, Nicholas Dronen · 2022 · arXiv
Fast approximations to matrix multiplication have the potential to dramatically reduce the cost of neural network inference. Recent work on approximate matrix multiplication proposed to replace costly multiplications with table-lookups by fitting a fast hash function from training data. In this work, we propose improvements to this previous work, targeted to the deep learning inference setting, where one has access to both training data and fixed (already learned) model weight matrices. We further propose a fine-tuning procedure for accelerating entire neural networks while minimizing loss in
Negative / Null Result ReportOpen accessComputer Science
Xinyan Hu, Meena Jagadeesan, Michael I. Jordan et al. · 2023 · arXiv
In content recommender systems such as TikTok and YouTube, the platform's recommendation algorithm shapes content producer incentives. Many platforms employ online learning, which generates intertemporal incentives, since content produced today affects recommendations of future content. We study the game between producers and analyze the content created at equilibrium. We show that standard online learning algorithms, such as Hedge and EXP3, unfortunately incentivize producers to create low-quality content, where producers' effort approaches zero in the long run for typical learning rate sched
Negative / Null Result ReportOpen accessComputer Science
Anqi Mao, Mehryar Mohri, Yutao Zhong · 2024 · arXiv
We present a detailed study of $H$-consistency bounds for regression. We first present new theorems that generalize the tools previously given to establish $H$-consistency bounds. This generalization proves essential for analyzing $H$-consistency bounds specific to regression. Next, we prove a series of novel $H$-consistency bounds for surrogate loss functions of the squared loss, under the assumption of a symmetric distribution and a bounded hypothesis set. This includes positive results for the Huber loss, all $\ell_p$ losses, $p \geq 1$, the squared $ε$-insensitive loss, as well as a negati
Negative / Null Result ReportOpen accessComputer Science
Hans-Joachim Böckenhauer, Elisabet Burjons, Martin Raszyk et al. · 2018 · arXiv
Parameterized complexity allows us to analyze the time complexity of problems with respect to a natural parameter depending on the problem. Reoptimization looks for solutions or approximations for problem instances when given solutions to neighboring instances. We try to combine both techniques, in order to better classify the complexity of problems in the parameterized setting. Specifically, we see that some problems in the class of compositional problems, which do not have polynomial kernels under standard complexity-theoretic assumptions, do have polynomial kernels under reoptimization for
Negative / Null Result ReportOpen accessPhysics
G. Maciejewski · 2022 · arXiv
Uninterrupted observations from space-borne telescopes provide the photometric precision that is required to detect shallow transits of small planets missed by ground-based surveys. We used data from the Transiting Exoplanet Survey Satellite (TESS) to search for nearby planetary companions in 12 planetary systems with hot Jupiters: HD 2685, Qatar-10, WASP-4, WASP-48, WASP-58, WASP-91, WASP-120, WASP-121, WASP-122, WASP-140, XO-6, and XO-7. We also applied the transit timing method based on homogeneously determined mid-transit times in order to search for non-transiting companions that could gr
Negative / Null Result ReportOpen accessComputer Science
Ali Çivril · 2017 · arXiv
It is well known that sparse approximation problem is \textsf{NP}-hard under general dictionaries. Several algorithms have been devised and analyzed in the past decade under various assumptions on the \emph{coherence} $μ$ of the dictionary represented by an $M \times N$ matrix from which a subset of $k$ column vectors is selected. All these results assume $μ=O(k^{-1})$. This article is an attempt to bridge the big gap between the negative result of \textsf{NP}-hardness under general dictionaries and the positive results under this restrictive assumption. In particular, it suggests that the afo
Abandoned HypothesisOpen accessComputer Science
S. J. van Enk · 2018 · arXiv
The phase factor $(-1)^{2s}$ that features in the exchange symmetry for identical spin-$s$ fermions or bosons is not simply and automatically equal to the phase factor one can observe in an interference experiment that involves physically exchanging two such particles. The observable phase contains, in general, single-particle geometric and dynamical phases as well, induced by both spin and spatial exchange transformations. By extending the analysis to (non-abelian) anyons it is argued that, similarly, there are single-anyon geometric and dynamical contributions in addition to purely topologic
Negative / Null Result ReportOpen accessMathematics
Yossi Arjevani, Ohad Shamir · 2016 · arXiv
Finite-sum optimization problems are ubiquitous in machine learning, and are commonly solved using first-order methods which rely on gradient computations. Recently, there has been growing interest in \emph{second-order} methods, which rely on both gradients and Hessians. In principle, second-order methods can require much fewer iterations than first-order methods, and hold the promise for more efficient algorithms. Although computing and manipulating Hessians is prohibitive for high-dimensional problems in general, the Hessians of individual functions in finite-sum problems can often be effic
Negative / Null Result ReportOpen accessComputer Science
Guy Van den Broeck, Adnan Darwiche · 2013 · arXiv
Lifted inference algorithms exploit symmetries in probabilistic models to speed up inference. They show impressive performance when calculating unconditional probabilities in relational models, but often resort to non-lifted inference when computing conditional probabilities. The reason is that conditioning on evidence breaks many of the model's symmetries, which can preempt standard lifting techniques. Recent theoretical results show, for example, that conditioning on evidence which corresponds to binary relations is #P-hard, suggesting that no lifting is to be expected in the worst case. In
Negative / Null Result ReportOpen accessComputer Science
Davin Choo, Kirankumar Shiragur · 2023 · arXiv
Recovering causal relationships from data is an important problem. Using observational data, one can typically only recover causal graphs up to a Markov equivalence class and additional assumptions or interventional data are needed for complete recovery. In this work, under some standard assumptions, we study causal graph discovery via adaptive interventions with node-dependent interventional costs. For this setting, we show that no algorithm can achieve an approximation guarantee that is asymptotically better than linear in the number of vertices with respect to the verification number; a wel
Negative / Null Result ReportOpen accessComputer Science
Valerio Varricchio, Brian Paden, Dmitry Yershov et al. · 2017 · arXiv
Nearest-neighbor search dominates the asymptotic complexity of sampling-based motion planning algorithms and is often addressed with k-d tree data structures. While it is generally believed that the expected complexity of nearest-neighbor queries is $O(log(N))$ in the size of the tree, this paper reveals that when a classic k-d tree approach is used with sub-Riemannian metrics, the expected query complexity is in fact $Θ(N^p \log(N))$ for a number $p \in [0, 1)$ determined by the degree of nonholonomy of the system. These metrics arise naturally in nonholonomic mechanical systems, including cl
Negative / Null Result ReportOpen accessComputer Science
Alejandro Alonso-Valero, Daniel Berzal-Rozalén, Felipe J. Llanes-Estrada et al. · 2024 · arXiv
We deploy the Hartree-Fock approximation for all-heavy quark hadrons, including quarkonium, baryons, tetraquarks, pentaquarks, dibaryons and up to the 12-body dibaryon-antidibaryon which completely fill the $1s$ orbital, in a unified manner, with the spinless LO Coulomb interaction and beyond. After treating the $c$ and $b$ quarks in various combinations, we delve a bit longer on $t$-quark bound states. We extend the negative result of Kuchiev, Flambaum and Shuryak on the 12-body topball to now include the NLO QCD potential. We find that none of the examined multitop states should have binding
