196,341 research outputs found
Reeh-Schlieder defeats Newton-Wigner: On alternative localization schemes in relativistic quantum field theory
No full textMany of the "counterintuitive" features of relativistic quantum field theory have their formal root in the Reeh-Schlieder theorem, which in particular entails that local operations applied to the vacuum state can produce any state of the entire field. It is of great interest then that I.E. Segal and, more recently, G. Fleming (in a paper entitled "Reeh-Schlieder meets Newton-Wigner") have proposed an alternative "Newton-Wigner" localization scheme that avoids the Reeh-Schlieder theorem. In this paper, I reconstruct the Newton-Wigner localization scheme and clarify the limited extent to which it avoids the counterintuitive consequences of the Reeh-Schlieder theorem. I also argue that there is no coherent interpretation of the Newton-Wigner localization scheme that renders it free from act-outcome correlations at spacelike separation
Reeh-Schlieder meets Newton-Wigner
No full textThe Reeh-Schlieder theorem asserts the vacuum and certain other states to be spacelike superentangled relative to local fields. This motivates an inquiry into the physical status of various concepts of localization. It is argued that a covariant generalization of Newton-Wigner localization is a physically illuminating concept. When analyzed in terms of nonlocally covariant quantum fields, creating and annihilating quanta in Newton-Wigner localized states, the vacuum is seen to not possess the spacelike superentanglement that the Reeh-Schlieder theorem displays relative to local fields, and to be locally empty as well as globally empty. Newton-Wigner localization is then shown to be physically interpretable in terms of a covariant generalization of the center of energy, the two localizations being identical if the system has no internal angular momentum. Finally, some of the counterintuitive features of Newton-Wigner localization are shown to have close analogues in classical special relativity
Receptive vocabulary development in sensorineural hearing-impaired children
No full textObjective. The aim of this study was to assess receptive vocabulary development in children with aided residual hearing, but without major co-morbidities. Patients and Methods. A total of 26 boys and 27 girls (tl: 2.0-7.4 years old) with bilateral sensorineural hearing loss (average at frequencies of 0.5,1, 2,4 kHz >21 dB in the better hearing ear) were recruited out of the 1994 implemented Gottinger Hor-Sprachregister (Go HSR). The mean age at diagnosis was 51.4 months (SD 19.6; min. 14; max. 85), the mean hearing aiding age: 51.9 months (SD 19.6). The children had an average nonverbal intelligence in Raven's Coloured Progressive Matrices and in CNIMS respectively. The individual assessment of receptive vocabulary was carried out at three time points using standardized test measures. The raw test scores were converted to T-scores (M=50; SD=10; normed for hearing children). The first psychometric examination took place after the ascertainment of the hearing loss (tl). Two follow-ups (t2, t3) were performed at 69 month time intervals. Results. No child with a hearing loss >61 dB HL obtained an age appropriate receptive vocabulary score. On average, the study group exhibited an age-delayed lexical performance at tl (M=38.7; SD=14.7) which significantly improved overtime reaching the lower norm level at t3 (M=44.7; SD=18.0; p70 dB HL) did not increase. Conclusion. Even a hearing loss <40 dB may negatively affect receptive vocabulary development. Receptive vocabulary outcome was not highly variable
Long-term follow-up of oral language development in children with permanent bilateral hearing loss
No full textObjective: The aim of this study was to assess the oral language development of children with permanent bilateral hearing loss without additional disabilities longitudinally (5 time points t1-t5). Method: The present follow-up study evaluated both receptive and expressive language developmental quotients (DQ; desired value 1.0) with standardised developmental scales and receptive and expressive vocabulary size with standardised tests (results in T-scores; m=50, SD=10). Mean follow-up duration was 38.1 (SD 4.8) months. Sample: A cohort of n=18 sensorineural hearing-impaired children was recruited from the German Gottinger Hor-Sprachregister. Mean diagnosis age was 21.4 (SD 16.6) months and mean age of amplification with hearing aids was 21.7 (SD 16.5) months. Results: The mean DQs slowly increased from t1 to t4 (DQ receptive 0.37/0.48/0.55/0.56; DQ expressive: 0.51/0.51/0.55/0.55) and remained norm deviant. The diagnosis age of hearing loss and both the developmental quotients for receptive (-0.41/-0.42/-0.53; p 90dB who all had received a cochlear-implant up to t3. Children who were identified as hearing-impaired before the age of 18 months exhibited on average generally greater DQs. Conclusion: The individual best available amplification of hearing loss did not compulsively cause an age-adequate spoken language development, at least not in case of a hearing loss > 40dB. So a newborn hearing screening must be the first step in identification, intervention and habilitation of an infant with hearing loss. Use of a cochlear implant seemed to have a great impact on the oral language development of children with a bilateral loss > 90 dB
Umweltgeschichte durch starke Disziplinen - Vom richtigen und falschen Einsatz der Interdisziplinarität
No full textUmweltgeschichte durch starke Disziplinen - Vom richtigen und falschen Einsatz der Interdisziplinarität
No full textOn the basis of the burnside ring of a fusion system
No full textWe consider the Burnside ring A(F) of F-stable S-sets for a saturated fusion system F defined on a p-group S. It is shown by S.P. Reeh that the monoid of F-stable sets is a free commutative monoid with canonical basis {αP}. We give an explicit formula that describes αP as an S-set. In the formula we use a combinatorial concept called broken chains which we introduce to understand inverses of modified Möbius functions. © 2014 Elsevier Inc
Microlocal analysis of quantum fields on curved space–times: Analytic wave front sets and Reeh–Schlieder theorems
No full textWe show in this article that the Reeh-Schlieder property holds for states of quantum fields on real analytic curved space-times if they satisfy an analytic microlocal spectrum condition. This result holds in the setting of general quantum field theory, i.e., without assuming the quantum field to obey a specific equation of motion. Moreover, quasifree states of the Klein-Gordon field are further investigated in the present work and the (analytic) microlocal spectrum condition is shown to be equivalent to simpler conditions. We also prove that any quasifree ground or KMS state of the Klein-Gordon field on a stationary real analytic space-time fulfills the analytic microlocal spectrum condition. (C) 2002 American Institute of Physics
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