All articles starting with P
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Positive energy theorem
The positive energy theorem, also called the positive mass theorem, states that an isolated system in general relativity has nonnegative total mass-energy, with equality only for flat Minkowski spacetime.
Positive externality
A positive externality is a benefit from one agent's production or consumption that lands on third parties, so markets underproduce goods such as vaccination, education, and research.
Positive feedback
Positive feedback is a loop in which a change in a system is amplified, moving it away from equilibrium, as in blood clotting and climate warming.
Positive Group
Positive Group, formerly Sarbacane Group, is a French marketing-technology SaaS company founded in 2001, headquartered in Hem near Lille and majority-owned by founder Mathieu Tarnus.
Positive Image Consulting Services Inc
Positive Image Consulting Services Inc is a company known only from an April 2025 SEC filing, which aggregator Provath records as $110 million raised; Ann Barlow is the only person named.
Positive liberty
Positive liberty, also called positive freedom, is the ability to achieve self-mastery and self-determination, one of two concepts of liberty distinguished by Isaiah Berlin in 1958.
Positive matrix factorization
Positive matrix factorization (PMF) is a non-negative matrix factorization method, introduced by Paatero and Tapper in 1994, that decomposes environmental measurements into source profiles and contributions, weighting each data point by its uncertainty.
Positive occult blood in stool
Positive occult blood in stool: a fecal occult blood test (FOBT, gFOBT, or FIT) has found hidden blood, signaling digestive tract bleeding from hemorrhoids, polyps, ulcers, or colorectal cancer; colonoscopy follow-up is standard.
Positive operator-valued measure
A positive operator-valued measure, or POVM, is the most general mathematical description of a quantum measurement, a set of positive semidefinite operators summing to the identity.
Positive position feedback
Positive position feedback (PPF) is a resonant control technique that actively damps vibration in flexible structures, introduced by Goh and Caughey in 1985 for large space structures.
Positive psychology
Positive psychology, launched by Martin Seligman's 1998 APA address and the 2000 Seligman–Csikszentmihalyi manifesto, studies well-being, character strengths, and PERMA; its interventions show modest effects and draw sustained criticism.
Positive psychotherapy
Positive psychotherapy is a strength-based therapy for depression that builds positive emotions, character strengths, and meaning, introduced by Martin Seligman, Tayyab Rashid, and Acacia Parks in 2006.
Positive sputum culture
Positive sputum culture: growth of pathogenic bacteria or fungi from coughed-up lung mucus (phlegm), used to diagnose pneumonia, tuberculosis, and bronchiectasis; interpretation limited by oropharyngeal contamination and prior antibiotics.
Positive staining
Positive staining is a microscopy contrast method in which heavy-metal salts bind directly to the specimen, so it appears dark against a light background in the image.
Positive Sum Capital
Positive Sum Capital is a venture capital firm founded in 2020 and based in Greenwich, Connecticut, led by CEO Patrick W. O'Shaughnessy and investing in early-stage technology companies.
Positive throat culture
A positive throat culture is a laboratory result showing group A Streptococcus growing from a throat swab, confirming strep throat and usually leading to antibiotics.
Positive train control
Positive train control (PTC) is a communications-based rail safety system, mandated by the Rail Safety Improvement Act of 2008, that automatically slows or stops trains not operated safely.
Positive-definite kernel
A positive-definite kernel is a symmetric function whose Gram matrix on any finite set of points is positive semidefinite, used in Gaussian processes and machine learning.
Positive-strand RNA virus
Positive-strand RNA virus (Group IV, +ssRNA): virus with messenger-sense RNA genome translated directly on entry; includes SARS-CoV-2, HCV, dengue, poliovirus. Replicates via dsRNA intermediate in membrane replication organelles; most lack proofreading, coronaviruses excepted.
Positive-unlabeled learning
Positive-unlabeled learning is a machine learning method that trains a binary classifier from only positive and unlabeled examples, used when negative data is unavailable or too costly to collect.
Positively Yours (아기가 생겼어요)
Positively Yours (아기가 생겼어요, Agiga Saenggyeosseoyo) is a 2026 Channel A romantic comedy drama adapted from Lee Jeong and Kang Ki's Naver webcomic. 12 episodes, January 17 to February 22, 2026; stars Choi Jin-hyuk and Oh Yeon-seo; Nielsen ratings in the 1% range but #1 on Rakuten Viki in 87 countries.
Positivism
Positivism, especially logical positivism (logical empiricism, neopositivism), is the 20th-century movement of the Vienna Circle (Schlick, Carnap, Neurath) and Berlin Circle (Reichenbach), holding knowledge is analytic or empirically verifiable and metaphysics meaningless; it declined by the 1960s.
Positivism in Poland
Positivism in Poland (pozytywizm polski), also called Warsaw positivism, was an intellectual and literary movement from the collapse of the January Uprising in 1864 to about 1890.
Positivist calendar
The Positivist calendar (Calendrier positiviste) is a calendar reform proposed by Auguste Comte in 1849, with 13 months of 28 days named for figures like Moses and Shakespeare.
Positivist Church of Humanity (Brazil)
The Positivist Church of Humanity (Igreja Positivista do Brasil) is a Brazilian religious institution founded in Rio de Janeiro in 1881 by followers of Auguste Comte.
Positivo Tecnologia
Positivo Tecnologia is a Brazilian technology company headquartered in Curitiba, founded in 1989 as Positivo Informática, that makes computers, servers, payment terminals, and education technology and provides IT services.
Pósito
A pósito was a municipal grain-storage institution of the preindustrial Spanish world, emerging in 15th-century Castile and spread to Spanish America to regulate the grain supply of colonial cities.
Positron
The positron, also called the antielectron, is the electron's antiparticle, with equal mass and a positive charge. Carl D. Anderson discovered it in cosmic rays in 1932.
Positron AI
Positron AI is an American AI inference hardware startup founded in 2023 by former Lambda and Groq employees, selling the Atlas inference system and developing custom silicon called Asimov.
Positron annihilation lifetime spectroscopy
Positron annihilation lifetime spectroscopy (PALS), a branch of positron annihilation spectroscopy, measures positron lifetimes in materials to characterize vacancy-type defects, free volume, and porosity at the sub-nanometer scale.