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Friday, October 28, 2011
peaceful nature background
This dichotomy between background dependent and independent theories is sometimes traced back as far as the antagonism between Newton and Leibniz about absolute vs. relational space. Most physicists would claim that the choice of approach is merely philosophical so far as no different falsifiable claims follow, not unlike the question of interpretations of quantum mechanics. However, two philosophers of science, Imre Lakatos and Elie Zahar, have argued that research programs can be driven by metaphysical questions and so adopting the view of background independence may lead to different results.
This is not a suggestion that spacetime is uniform, merely that the fundamental rules governing the measurable characteristics of the physical universe are the same everywhere, at all times.
One of the major shortcomings of loop quantum gravity is that, as of 2009, it has not been shown that the theory in fact reduces to Einstein's general relativity in the continuum limit. Since GR equations were used initially to construct the theory, many researchers assume that they can be recovered, but this has neither been explicitly proved nor disproved. In addition, incorporating matter into the theory is an ongoing problem.
Assume pure gravity first. Say we have two coordinate systems, x-coordinates and y-coordinates. General covariance demands the equations of motion have the same form in both coordinate systems, that is, we have exactly the same differential equation to solve in both coordinate systems, except in one the independent variable is x and in the other it is y. Once we find a metric function gab(x) that solves the EOM in the x-coordinates we immediately know (by exactly the same reasoning as above!) that the same function written as a function of y solves the EOM in the y-coordinates. As both metric functions have the same functional form but belong to different coordinate systems, they impose different spacetime geometries. Thus we have generated a second distinct solution!
Although the physics of string theory can in principle be background-independent, perturbative formulations of this theory do not make this independence manifest because they require starting with a particular solution and performing a perturbative expansion about this background. Non-perturbative formulations such as matrix theory and AdS/CFT resolve that issue and are fully background independent.
This is not a suggestion that spacetime is uniform, merely that the fundamental rules governing the measurable characteristics of the physical universe are the same everywhere, at all times.
One of the major shortcomings of loop quantum gravity is that, as of 2009, it has not been shown that the theory in fact reduces to Einstein's general relativity in the continuum limit. Since GR equations were used initially to construct the theory, many researchers assume that they can be recovered, but this has neither been explicitly proved nor disproved. In addition, incorporating matter into the theory is an ongoing problem.
Assume pure gravity first. Say we have two coordinate systems, x-coordinates and y-coordinates. General covariance demands the equations of motion have the same form in both coordinate systems, that is, we have exactly the same differential equation to solve in both coordinate systems, except in one the independent variable is x and in the other it is y. Once we find a metric function gab(x) that solves the EOM in the x-coordinates we immediately know (by exactly the same reasoning as above!) that the same function written as a function of y solves the EOM in the y-coordinates. As both metric functions have the same functional form but belong to different coordinate systems, they impose different spacetime geometries. Thus we have generated a second distinct solution!
Although the physics of string theory can in principle be background-independent, perturbative formulations of this theory do not make this independence manifest because they require starting with a particular solution and performing a perturbative expansion about this background. Non-perturbative formulations such as matrix theory and AdS/CFT resolve that issue and are fully background independent.
Thursday, October 27, 2011
images autumn backgrounds
From Tara it was borrowed (or taken) around the year 600 AD to Scotland where it soon found a place of honour in Scone – and, once there, Scottish Kings were crowned upon it. In 1296, Edward the First conquered Scotland – and his greatest prize was the Stone of Scone – Jacob's Pillow! A coronation throne was constructed to accommodate the stone (the British Monarch wouldn’t deign to actually sit on a rock itself). Jacob's Pillow stayed in England for the next six hundred and fifty-plus years.
Lots of ideas for Rare Dreams are flying around between us and Sonum is already working on some music and songs. In this project you can expect to be amazingly stretched as a singer, actor, dancer, musician, writer or poet. And the way we work creates an atmosphere of trust and safety as well as fun and joy. It's an incredible adventure for us all and we are looking forward to it already."
Goblin Market - adapted by Kath Burlinson from the poem by Christina Rosetti composed by Conor Mitchell The Edinburgh Festival run of Goblin Market finished on 28 August 2005 after a 21 performance run lasting over a month. The production received many 4 and 5 star reviews and was seen by over 2,500 people.
Quantum 3 - directed by Jaki McCarrick Working around a prepared libretto, the team that brought 'Fridge', a hilarious and zany musical piece, to the parting shots of the National Student Drama Festival in April, workshop and stage their brand new work. Belfast participants will be involved in the theatre making process from start to finish. There will be skills enhancement in song writing, lyric writing, musical theatre performance, choreography and movement, and in drama (Stanislavski based, scene-work and improvisation). It promises to be a rigorous, exciting week.
No Stone Unturned - book and lyrics by Dave Hudson composed by Denise Wright The story of Jacob's Pillow is a legend that extends back to biblical times. The stone is reputed to have originated in the desert with Jacob himself, travelled o Jerusalem, from there to Spain and eventually Ireland at the legendary Tara where kings who were crowned upon it were said to be assured of longer lives.
Lots of ideas for Rare Dreams are flying around between us and Sonum is already working on some music and songs. In this project you can expect to be amazingly stretched as a singer, actor, dancer, musician, writer or poet. And the way we work creates an atmosphere of trust and safety as well as fun and joy. It's an incredible adventure for us all and we are looking forward to it already."
Goblin Market - adapted by Kath Burlinson from the poem by Christina Rosetti composed by Conor Mitchell The Edinburgh Festival run of Goblin Market finished on 28 August 2005 after a 21 performance run lasting over a month. The production received many 4 and 5 star reviews and was seen by over 2,500 people.
Quantum 3 - directed by Jaki McCarrick Working around a prepared libretto, the team that brought 'Fridge', a hilarious and zany musical piece, to the parting shots of the National Student Drama Festival in April, workshop and stage their brand new work. Belfast participants will be involved in the theatre making process from start to finish. There will be skills enhancement in song writing, lyric writing, musical theatre performance, choreography and movement, and in drama (Stanislavski based, scene-work and improvisation). It promises to be a rigorous, exciting week.
No Stone Unturned - book and lyrics by Dave Hudson composed by Denise Wright The story of Jacob's Pillow is a legend that extends back to biblical times. The stone is reputed to have originated in the desert with Jacob himself, travelled o Jerusalem, from there to Spain and eventually Ireland at the legendary Tara where kings who were crowned upon it were said to be assured of longer lives.
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