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Benvenuti in queste pagine dedicate a scienza, storia ed arte. Amelia Carolina Sparavigna, Torino

Friday, April 29, 2011

Noether's (first) theorem

"Noether's (first) theorem states that any differentiable symmetry of the action of a physical system has a corresponding conservation law. The theorem was proved by German mathematician Emmy Noether in 1915 and published in 1918.[1] The action of a physical system is the integral over time of a Lagrangian function (which may or may not be an integral over space of a Lagrangian density function), from which the system's behavior can be determined by the principle of least action.
Noether's theorem has become a fundamental tool of modern theoretical physics and the calculus of variations. A generalization of the seminal formulations on constants of motion in Lagrangian and Hamiltonian mechanics (1788 and 1833, respectively), it does not apply to systems that cannot be modeled with a Lagrangian; for example,dissipative systems with continuous symmetries need not have a corresponding conservation law." Wikipedia, l'enciclopedia libera.

Emmy Noether

Professor Einstein Writes in Appreciation of a Fellow-Mathematician.

To the Editor of The New York Times:
The efforts of most human-beings are consumed in the struggle for their daily bread, but most of those who are, either through fortune or some special gift, relieved of this struggle are largely absorbed in further improving their worldly lot. Beneath the effort directed toward the accumulation of worldly goods lies all too frequently the illusion that this is the most substantial and desirable end to be achieved; but there is, fortunately, a minority composed of those who recognize early in their lives that the most beautiful and satisfying experiences open to humankind are not derived from the outside, but are bound up with the development of the individual's own feeling, thinking and acting. The genuine artists, investigators and thinkers have always been persons of this kind. However inconspicuously the life of these individuals runs its course, none the less the fruits of their endeavors are the most valuable contributions which one generation can make to its successors.
Within the past few days a distinguished mathematician, Professor Emmy Noether, formerly connected with the University of Göttingen and for the past two years at Bryn Mawr College, died in her fifty-third year. In the judgment of the most competent living mathematicians, Fräulein Noether was the most significant creative mathematical genius thus far produced since the higher education of women began. In the realm of algebra, in which the most gifted mathematicians have been busy for centuries, she discovered methods which have proved of enormous importance in the development of the present-day younger generation of mathematicians. Pure mathematics is, in its way, the poetry of logical ideas. One seeks the most general ideas of operation which will bring together in simple, logical and unified form the largest possible circle of formal relationships. In this effort toward logical beauty spiritual formulas are discovered necessary for the deeper penetration into the laws of nature.
Born in a Jewish family distinguished for the love of learning, Emmy Noether, who, in spite of the efforts of the great Göttingen mathematician, Hilbert, never reached the academic standing due her in her own country, none the less surrounded herself with a group of students and investigators at Göttingen, who have already become distinguished as teachers and investigators. Her unselfish, significant work over a period of many years was rewarded by the new rulers of Germany with a dismissal, which cost her the means of maintaining her simple life and the opportunity to carry on her mathematical studies. Farsighted friends of science in this country were fortunately able to make such arrangements at Bryn Mawr College and at Princeton that she found in America up to the day of her death not only colleagues who esteemed her friendship but grateful pupils whose enthusiasm made her last years the happiest and perhaps the most fruitful of her entire career.

Albert  Einstein.
Princeton University, May 1, 1935.
[The New York Times May 5, 1935]

Thursday, April 28, 2011

Hokusai manga - fox



Hokusai manga
Museo Arte Orientale, Torino




Four actors



A group of four actors
Tang Dinasty, first half of the 8th century AD
Museo Arte Orientale, Torino

Padmapani


Padmapani
Gandhara, II-III secolo d.C.

Il Bodhisattva Padmapani siede su un alto trono con il piede sinistro posato a terra e la gamba destra piegata a appoggiata sul ginocchio opposto. L’alto seggio su cui Padmapani è seduto ha una spessa base su cui si appoggiano i sandali (infradito!). Il Bodhisattva indossa paridhana e uttariya. Porta un turbante a fascia, grandi orecchini a testa di leone, collane e un cordone con piccoli involucri porta-preghiere, portato di traverso dalla spalla sinistra al fianco destro. Padmapani tiene nella mano sinistra un grosso bocciolo di fiore di loto, mentre l’altra, mancante, era rivolta verso la testa.

Museo Arte Orientale, Torino


Il funzionario


Funzionario militare
Dinastia Tang, VIII secolo D.C.
Terracotta rossa, ingobbio bianco, pigmenti e oro
Military official
Tang Dinasty 8th centry A.D.
Red earthenware with white engobe, pigments and gold



Museo Arte Orientale, Torino

Thermal barrier coating could boost efficiency of gas turbines

"A spin-out company from Imperial College London has developed a thermal barrier coating for gas turbine parts that can optically feed back its temperature and ageing status even while the engine is running at full speed.
The main application for the technology is in power-generating gas turbines, where the coating could help to achieve significant efficiency savings.
Ceramic thermal barrier coatings, including yttria-stabilised zirconia, are used for the so-called ‘hot section components’ of gas turbines, such as the blades." Thermal barrier coating could boost efficiency of gas turbines | News | The Engineer

Tuesday, April 26, 2011

Poems









Stampe xilografiche, Giappone, Periodo Edo
Museo Arte Orientale, Torino

Crabs use stats

News in Science
Crabs use stats to dodge predators
Monday, 18 April 2011 Anna Salleh
ABC


Fiddler crabs can't see very well so they have to use statistical calculations to distinguish between swooping predators and harmless passing insects, say researchers.

I granchi e la statistica

"I granchi della famiglia Ocypodidae, per via della loro scarsa capacità visiva, sono in grado di calcolare la probabilità che l'oggetto che stanno osservando possa essere un predatore... Gli occhi di questi granchi sono dotati di una bassissima risoluzione, pari a circa un totale di 8.000 pixel per ogni occhio.... A questa risoluzione, un predatore come un uccello è visibile sotto forma di un semplice e insignificante puntino scuro, e non è possibile distinguere se si tratta di un animale innocuo o potenzialmente pericoloso.  Per ovviare alla loro ridotta capacità visiva, i granchi hanno quindi elaborato una strategia che consente loro di calcolare la probabilità che uno di questi puntini scuri possa essere un predatore." by Dita di Fulmine
http://www.ditadifulmine.com/2011/04/granchi-usano-statistica-per-rilevare.html