Detection of negative energy: 4-dimensional examples

We study the response of switched particle detectors to static negative energy densities and negative energy fluxes. It is demonstrated how the switching leads to excitation even in the vacuum and how negative energy can lead to a suppression of this excitation. We obtain quantum inequalities on the detection similar to those obtained for the energy density by Ford and co-workers and in an `operational' context by Helfer. We revisit the question `Is there a quantum equivalence principle?' in terms of our model. Finally, we briefly address the issue of negative energy and the second law of thermodynamics.Comment: 10 pages, 7 figure

Quantum inequalities in two dimensional curved spacetimes

We generalize a result of Vollick constraining the possible behaviors of the renormalized expected stress-energy tensor of a free massless scalar field in two dimensional spacetimes that are globally conformal to Minkowski spacetime. Vollick derived a lower bound for the energy density measured by a static observer in a static spacetime, averaged with respect to the observers proper time by integrating against a smearing function. Here we extend the result to arbitrary curves in non-static spacetimes. The proof, like Vollick's proof, is based on conformal transformations and the use of our earlier optimal bound in flat Minkowski spacetime. The existence of such a quantum inequality was previously established by Fewster.Comment: revtex 4, 5 pages, no figures, submitted to Phys. Rev. D. Minor correction

Quantum inequalities and `quantum interest' as eigenvalue problems

Quantum inequalities (QI's) provide lower bounds on the averaged energy density of a quantum field. We show how the QI's for massless scalar fields in even dimensional Minkowski space may be reformulated in terms of the positivity of a certain self-adjoint operator - a generalised Schroedinger operator with the energy density as the potential - and hence as an eigenvalue problem. We use this idea to verify that the energy density produced by a moving mirror in two dimensions is compatible with the QI's for a large class of mirror trajectories. In addition, we apply this viewpoint to the `quantum interest conjecture' of Ford and Roman, which asserts that the positive part of an energy density always overcompensates for any negative components. For various simple models in two and four dimensions we obtain the best possible bounds on the `quantum interest rate' and on the maximum delay between a negative pulse and a compensating positive pulse. Perhaps surprisingly, we find that - in four dimensions - it is impossible for a positive delta-function pulse of any magnitude to compensate for a negative delta-function pulse, no matter how close together they occur.Comment: 18 pages, RevTeX. One new result added; typos fixed. To appear in Phys. Rev.

Longitudinal Study on the Performance of U.S. Pharmaceutical Firms: The Increasing Role of Marketing

Nowadays, the U.S. pharmaceutical industry has been under thorough scrutiny. Popular press claims of intensive marketing activities that go beyond R&D, the strong increase of me-too drugs, and, at the same time, the high industry profitability have contributed to public skepticism. Despite this increasing role of marketing, studies on the profitability of pharmaceutical firms mainly focus on the role of R&D. In this paper, we investigate the impact of advertising and product differentiation on pharmaceutical firms’ market value over the period 1971-2005. Especially, we examine whether there has been a change in the pattern of returns in these variables over this period. Our results show that, nowadays, pharmaceutical firms’ performance is not only closely linked to their R&D activities but also to marketing activities such as advertising and product differentiation. Since the 1990s, the return of advertising has become three times larger than that of R&D. In addition, we found that the impact of product differentiation came largely from the introduction of the so called incrementally modified drugs (IMD). The vast increase of the number of IMDs since the 1990s is likely to contribute to this development. Our results emphasize the role of advertising and product differentiation in the virtuous rent-seeking behavior in the pharmaceutical industry.Marketing;Panel data;Advertising;Market value;Pharmaceutical industry;Product differentiation

Quantum Field Theory Constrains Traversable Wormhole Geometries

Recently a bound on negative energy densities in four-dimensional Minkowski spacetime was derived for a minimally coupled, quantized, massless, scalar field in an arbitrary quantum state. The bound has the form of an uncertainty principle-type constraint on the magnitude and duration of the negative energy density seen by a timelike geodesic observer. When spacetime is curved and/or has boundaries, we argue that the bound should hold in regions small compared to the minimum local characteristic radius of curvature or the distance to any boundaries, since spacetime can be considered approximately Minkowski on these scales. We apply the bound to the stress-energy of static traversable wormhole spacetimes. Our analysis implies that either the wormhole must be only a little larger than Planck size or that there is a large discrepancy in the length scales which characterize the wormhole. In the latter case, the negative energy must typically be concentrated in a thin band many orders of magnitude smaller than the throat size. These results would seem to make the existence of macroscopic traversable wormholes very improbable.Comment: 26 pages, plain LaTe

Fast generation of 3D deformable moving surfaces

Dynamic surface modeling is an important subject of geometric modeling due to their extensive applications in engineering design, entertainment and medical visualization. Many deformable objects in the real world are dynamic objects as their shapes change over time. Traditional geometric modeling methods are mainly concerned with static problems, therefore unsuitable for the representation of dynamic objects. Apart from the definition of a dynamic modeling problem, another key issue is how to solve the problem. Because of the complexity of the representations, currently the finite element method or finite difference method is usually used. Their major shortcoming is the excessive computational cost, hence not ideal for applications requiring real-time performance. We propose a representation of dynamic surface modeling with a set of fourth order dynamic partial differential equations (PDEs). To solve these dynamic PDEs accurately and efficiently, we also develop an effective resolution method. This method is further extended to achieve local deformation and produce n-sided patches. It is demonstrated that this new method is almost as fast and accurate as the analytical closed form resolution method and much more efficient and accurate than the numerical methods

Socio-economic Analysis of Centralised Biogas Plants

The development of biogas technology in Denmark has been widely encouraged by the government over the last 15 years. The overall reasons for the government concern has been the increasing awareness that centralised biogas plants make a significant contribution to solve a range of problems in the fields of energy, agriculture and environment. This has been documented through related monitoring and R & D activities. To achieve a satisfactory evaluation of centralised biogas plants, a thorough socio – economic analysis is required. Such investigation has been accomplished, and the results are presented in this summary

Quantum interest in two dimensions

The quantum interest conjecture of Ford and Roman asserts that any negative-energy pulse must necessarily be followed by an over-compensating positive-energy one within a certain maximum time delay. Furthermore, the minimum amount of over-compensation increases with the separation between the pulses. In this paper, we first study the case of a negative-energy square pulse followed by a positive-energy one for a minimally coupled, massless scalar field in two-dimensional Minkowski space. We obtain explicit expressions for the maximum time delay and the amount of over-compensation needed, using a previously developed eigenvalue approach. These results are then used to give a proof of the quantum interest conjecture for massless scalar fields in two dimensions, valid for general energy distributions.Comment: 17 pages, 4 figures; final version to appear in PR

The Quantum Interest Conjecture

Although quantum field theory allows local negative energy densities and fluxes, it also places severe restrictions upon the magnitude and extent of the negative energy. The restrictions take the form of quantum inequalities. These inequalities imply that a pulse of negative energy must not only be followed by a compensating pulse of positive energy, but that the temporal separation between the pulses is inversely proportional to their amplitude. In an earlier paper we conjectured that there is a further constraint upon a negative and positive energy delta-function pulse pair. This conjecture (the quantum interest conjecture) states that a positive energy pulse must overcompensate the negative energy pulse by an amount which is a monotonically increasing function of the pulse separation. In the present paper we prove the conjecture for massless quantized scalar fields in two and four-dimensional flat spacetime, and show that it is implied by the quantum inequalities.Comment: 17 pages, Latex, 3 figures, uses eps

Defects, dopants and Li-ion diffusion in Li2SiO3

Запропонована логіко-структурна схема концепції управління інвестиційним забезпеченням промислового підприємства, яка враховує положення підприємства в зовнішньому та внутрішньому середовищах та підвищення ефективності його функціонування. Використання комплексного підходу щодо оцінки рівня інвестиційного забезпечення промислового підприємства дає можливість визначити позицію, яку воно посідає на конкурентному ринку і, відтак, сформувати необхідну для потенційного інвестора уяву про підприємство