Context and question: In general relativity, a vanishing stress-energy tensor implies, through Einstein field equations, the vanishing of all the components of the Ricci tensor. Vacuum does not mean that the curvature of space-time is necessarily flat: the gravitational field can still produce curvature in a vacuum in the form of tidal forces and gravitational waves (technically, these phenomena are the components of the Weyl tensor). The black hole (with zero electric charge) is an elegant example of a region completely "filled" with vacuum, but still showing a strong curvature.
what is a perfect example of a filled vacuum showing a curvature?
Answer: The black hole
Context and question: In the mid to late 1990s many higher-end AV receivers included the demodulator circuit specifically for the LaserDisc players RF modulated Dolby Digital AC-3 signal. By the late 1990s with LaserDisc players and disc sales declining due to DVD's growing popularity the AV receiver manufacturers removed the demodulator circuit. Although DVD players were capable of playing Dolby Digital tracks, the signal out of DVD player were not in a modulated form and not compatible with the inputs designed for LaserDisc AC-3. Outboard demodulators were available for a period that convert the AC-3 signal to standard Dolby Digital signal that was compatible with the standard Dolby Digital/PCM inputs on capable AV receivers. Another type marketed by Onkyo and others converted the RF AC-3 signal to 6-channel analog audio.
Did all AV receivers carry the demodulator circuits necessary for LaserDiscs, or only high-end models?
Answer: higher-end
Context and question: Hasidic or Chasidic Judaism overlaps significantly with Haredi Judaism in its engagement with the secular and commercial world, and in regard to social issues. It precedes the later and differs in its genesis and emerged focus. The movement originated in Eastern Europe (what is now Belarus and Ukraine) in the 18th century. Founded by Israel ben Eliezer, known as the Baal Shem Tov (1698–1760), it emerged in an age of persecution of the Jewish people, when a schism existed between scholarly and common European Jews. In addition to bridging this class gap, Hasidic teachings sought to reintroduce joy in the performance of the commandments and in prayer through the popularisation of Jewish mysticism (this joy had been suppressed in the intense intellectual study of the Talmud). The Ba'al Shem Tov sought to combine rigorous scholarship with more emotional mitzvah observance. In a practical sense, what distinguishes Hasidic Judaism from other forms of Haredi Judaism is the close-knit organization of Hasidic communities centered on a Rebbe (sometimes translated as "Grand Rabbi"), and various customs and modes of dress particular to each community. In some cases, there are religious ideological distinctions between Hasidic groups, as well. Another phenomenon that sets Hasidic Judaism apart from general Haredi Judaism is the strong emphasis placed on speaking Yiddish; in (many) Hasidic households and communities, Yiddish is spoken exclusively.
What is the spoken word known as in Hasidic Judiasm?
Answer:
Yiddish