Showing papers in "Lettere Al Nuovo Cimento in 1980"

A general argument against superluminal transmission through the quantum mechanical measurement process

Abstract: In a r ecen t pape r (1) two of us have shown t h a t some recen t resul ts (~-4) abou t t he poss ib i l i ty of t r a n s m i t t i n g super lumina l signals t h r o u g h the collapse of t he wave funct ion have been ob ta ined using incorrec t a rgument s , e i ther mak ing use of con t r ad i c to ry a s sumpt ions {3,4) or d i s regard ing the l imi ta t ions on the func t ion ing of a ha l f -wave p la te which follow f rom the a s sumed ro ta t iona l invar iance of t he t h e o r y (2). I n t he p r e s en t pape r we w a n t to po in t out t h a t no super lumina l t r ansmiss ion of signals can be ob ta ined as a consequence of the s t a n d a r d q u a n t u m thco ry of measm'ement . This fact will be shown to be t rue comple te ly in general , w i t h o u t resor t ing to t he Wigne r -Arak i -Yanase t h e o r e m (5,6) we have used in ref. (1). We s ta r t by observ ing t h a t t he above quo ted papers deal w i th a composi te q u a n t u m sys t em S -U + V for which thc t w o c o m p o n e n t subsys t ems U and V lie in largely s epa ra t ed space regions and arc non in te rac t ing . In these s epa ra t ed regions we h a v e two appa ra tuses A and B devised to pe r fo rm m e a s u r e m e n t s on U and V, respect ive ly .

On the structure of symplectic operators and hereditary symmetries

Abstract: In the last fifteen years, there has been a remarlmble development in the exact analysis of certain nonlinear evolution equations, like tbe Korteweg-de Vries equation. I t is weH known that among the surprising features of these so-called exactly solvable equations is the possession of infinitely many symmetries and conservation laws, of N-soliton solutions and Bäcklund transformations. It has turned out that considering an operator which maps symmetries (1) onto symmetries of a given equation yields a useful approach to all these features. 'l'his operator is called a strong synunetry (2 ) ( or recursion operator (3 ) ). It is particularly useful because its transpose generates conserved covariants from given ones and because its eigenfunctions are also symmetries (which actually characterize the N-soliton solutions). One way of finding strong symmetries is to use the fact that any translation-invariant operator fP(u), possessing the property defined by v below is a strong symmetry for the hierarchy of equations u, = ( fP(u) )\" Uz, n = 0, 1, 2, ... . These operators are called hereditary symmetries. The strong symmetries of all well-known exactly solvable equations are hereditary (2 ). Recently there has also been progress in understanding the Hamiltonian structure of these evolution equations (4). An evolution equations is said to be a Hamiltonian system if it can be written in the form u 1 = O(u)f(u), where O(u) is impletic (which is, roughly speaking, the same as saying that 0-1(u) is sympletic) and where f(u) is the gradient of a suitable potential. For these systems tbe operator-valued function O(u) is of particular interest because it is a N oether operator, i.e. it maps conserved covariants onto symmetries. Our paper is related to .1\\Iagri's work wbo considered bi-Hamiltonion systems u, = = 81(u)j1(u) = 82(u)/2(u) and who sbowed that these equations have fP(u) =81(u) 8;(u) as strong symmetries.

Measurements of < P T 2 > in and < P T 2 > out distributions in high-energy pp interactions

Abstract: The results of the present paper show that the « planarity » effects observed in the multiparticle systems produced in (e+e-) annihilations (1) are also present in the multiparticle systems produced in pp interactions. This means that the analogy already reported between pp interactions and (e+e-) annihilations, i) in the inclusiveXR* distributions (2) and ii) in the average charged-particle multiplicity (7),does in fact hold also iii) for the « planarity » structure of the multiparticle systems produced.

Quartet states in 20 Ne

Abstract: T rans f e r r eac t i ons of a, SBe a n d 12C c lus ters on N = Z e v e n e v e n t a rge t s (1) h a v e g i v e n e x p e r i m e n t a l s u p p o r t to t h e q u a r t e t model , f i rs t ly p roposed b y DA~OS a n d GILLET (2). I n t h i s work we h a v e inves t iga t ed , b y m e a n s of t he l~F(p, a)x60 reac t ion , t h e poss ible p resence of q u a r t e t s t a t e s in 2~ co r r e spond ing to exc i t a t i ons f r o m the (0p) to t h e (0d, ls) or (0], lp ) shells. E x c i t a t i o n func t i ons a n d a n g u l a r d i s t r i b u t i o n s r e l a t ive to t he t r a n s i t i o n s to t h e lowest levels in l~0(a0, ~ , a~, ~2, as) h a v e b e e n m e a s u r e d in t h e ene rgy r a n g e 0 . 7 0 < E r < 2 . 6 8 M e V , i .e . in t h e 2~ e x c i t a t i o n region E ~ = ( 1 3 . 5 -15.4) MeV, w h e r e t he b a n d h e a d of t h e 1211[ q u a r t e t conf igura t ion is p r e d i c t e d (3). T h e bas ic idea of t h i s work , t o g e t h e r w i t h t h e e x p e r i m e n t a l se t -up a n d t he f i rs t resul ts , h a s b e e n p r e s e n t e d e l sewhere (a). T he J ~ va lues of t h e i n t e r m e d i a t e s t a t e s

Lepton Self-mass, Higgs Scalar and Heavy-quark Masses

Abstract: In the last two years, it has been seen that experimental data [1] agreed very wellwith the Weinberg-Salam (W-S) [2] model, the SU(2) × U(1) gauge theory of weak andelectromagnetic interactions.Fundamentalfermions(point-likespin 1/2 leptons andquarks)are assumedto interactas left-handed weak isodoublets while the charged leptons and quarks are interacting asright-handed weak isosinglets in successive generations :(ν

Existence of a Lax pair for any member of the class of nonlinear evolution equations associated to the matrix Schrödinger spectral problem

Abstract: In recent years, th rough a genera l ized Wronskian technique, a large class of nonl inear evo lu t ion equat ions (hereafter referred to as CD class) associated to the m a t r i x SchrSdinger spect ra l p rob lem has been discovered, which can be solved by the inverse spectral t r ans fo rm (IST) (1). I n th is l e t te r we show tha t a L a x pa i r can be cons t ruc ted for any equa t ion of this class. This allows us to find out, for a g iven t ime evolu t ion of the (~ potent ia l ~), no t only the t ime evo lu t ion of the spectral data , b u t also the t i m e evolut ion of the e igenfunet ions of the associated l inear operator . We recal l t ha t s imilar findings, bu t for a subclass of CD, were prev ious ly achieved by iV~IODEK (2), while CASE and CHIC (3) ob ta ined the t ime evolu t ion of the e igenfunct ions in the scalar case. L e t us consider the ma t r ix SchrSdinger equa t ion

Study of (π+π-π+π-) and (π+π-π0) channel in e+e- annihilation at (1.450÷1.875) GeV cm. energy

Abstract: The study of (π+π-π+π-) and (π+π-π0) channel in e+e- annihilation at (1.450÷1.875) GeV cm. energy is presented