Exact Diagonalization of Two Quantum Models for the Damped Harmonic Oscillator

The damped harmonic oscillator is a workhorse for the study of dissipation in quantum mechanics. However, despite its simplicity, this system has given rise to some approximations whose validity and relation to more refined descriptions deserve a thorough investigation. In this work, we apply a method that allows us to diagonalize exactly the dissipative Hamiltonians that are frequently adopted in the literature. Using this method we derive the conditions of validity of the rotating-wave approximation (RWA) and show how this approximate description relates to more general ones. We also show that the existence of dissipative coherent states is intimately related to the RWA. Finally, through the evaluation of the dynamics of the damped oscillator, we notice an important property of the dissipative model that has not been properly accounted for in previous works; namely, the necessity of new constraints to the application of the factorizable initial conditions.Comment: 19 pages, 2 figures, ReVTe

Bacteriological And Clinical Evaluation Of Twelve Cases Of Post-Surgical Sepsis Of Odontogenic Tumors At A Referral Centre

Objective: To detennine the bacterial aetiology of sepsis occurring following surgery of odontogenic tumours and assess the effect of prompt and proper antibiotic usage. Desigu: A prospective study. Settiug: A tertiary referral centre in Lagos, Nigeria. . . Subjects: Twelve patients with odontogenic tumours that developed sepsis postoperatively. Eight of the patients were referred from private hospitals, the remaining were in-patients who sought for alternative medical attention following interruption of health care services at the referral cenlre. TutenJmtiou: Adequate review of patient's medical history, bacteriological investigations and antibiotic therapy. Mniu outcome measures: Bacteriological and clinic~! cure following antibiotic therapy based on susceptibility test results. Results: Two categories of patients were identified; those who completed the course of antibiotics prescribed post-surgery and patients who failed to conform to antibiotic prescription. Sepsis developed in the non-compliance group much earlier than in the group that complied (p<0.001). Infections were polybacterial with aerobes accounting for 77.4% (a-haemolytic streptococci 29.0%, Streptococcus pyogenes 16.1%, ~tapllylococcus aureus 16.1%, diphtheroids 9.7%, Klebsiella puemnouiae 6.5%) and anaerobes 22.6% (Porpltyromonas gingiva lis 9.7%, Peptostreptococcus spp. 6.5%, Prevotella melnninogenica 3.2%, Clostridium perfringeus 3.2%). Mixed aerobic and anaerobic aetiology occurred more in osteosarcoma and fibrosarcoma. Clostridium perfriugens was isolated from a case of osteosarcoma with necrotic tissues. The anaerobic bacteria were 100% sensitive to metronidazole, ciprolloxacin and augmentin, 65-85% sensitivity to ampicloxacillin, amoxicillin and erythromycin. Over 92% of the streptococci were sensitive to the P-Lactams contrast low susceptibility with S. aureus and K. pnemnoniae. Couclusion: Interruption of healthcare service was the sole factor identified in the development of sepsis as the patients could not be monitored to ensure compliance to prescriptio

Decoherence of molecular wave packets in an anharmonic potential

The time evolution of anharmonic molecular wave packets is investigated under the influence of the environment consisting of harmonic oscillators. These oscillators represent photon or phonon modes and assumed to be in thermal equilibrium. Our model explicitly incorporates the fact that in the case of a nonequidistant spectrum the rates of the environment induced transitions are different for each transition. The nonunitary time evolution is visualized by the aid of the Wigner function related to the vibrational state of the molecule. The time scale of decoherence is much shorter than that of dissipation, and gives rise to states which are mixtures of localized states along the phase space orbit of the corresponding classical particle. This behavior is to a large extent independent of the coupling strength, the temperature of the environment and also of the initial state.Comment: 7 pages, 4 figure

Hadron Spectra for Semileptonic Heavy Quark Decay

We calculate the leading perturbative and power corrections to the hadronic invariant mass and energy spectra in semileptonic heavy hadron decays. We apply our results to the $B$ system. Moments of the invariant mass spectrum, which vanish in the parton model, probe gluon bremsstrahlung and nonperturbative effects. Combining our results with recent data on $B$ meson branching ratios, we obtain a lower bound $\bar\Lambda>410\,{\rm MeV}$ and an upper bound $m_b^{\rm pole}<4.89\,$GeV. The Brodsky-Lepage-Mackenzie scale setting procedure suggests that higher order perturbative corrections are small for bottom decay, and even tractable for charm decay.Comment: 24 pages, uses REVTeX, 5 EPS figures embedded with epsf.sty, slightly modified version to appear in Phys. Rev.

B-->pi and B-->K transitions in standard and quenched chiral perturbation theory

We study the effects of chiral logs on the heavy-->light pseudoscalar meson transition form factors by using standard and quenched chiral perturbation theory combined with the static heavy quark limit. The resulting expressions are used to indicate the size of uncertainties due to the use of the quenched approximation in the current lattice studies. They may also be used to assess the size of systematic uncertainties induced by missing chiral log terms in extrapolating toward the physical pion mass. We also provide the coefficient multiplying the quenched chiral log, which may be useful if the quenched lattice studies are performed with very light mesons.Comment: 33 pages, 8 PostScript figures, version to appear in PR