Measurement of the space-time interval between two events using the retarded and advanced times of each event with respect to a time-like world-line

Several recent studies have been devoted to investigating the limitations that ordinary quantum mechanics and/or quantum gravity might impose on the measurability of space-time observables. These analyses are often confined to the simplified context of two-dimensional flat space-time and rely on a simple procedure for the measurement of space-like distances based on the exchange of light signals. We present a generalization of this measurement procedure applicable to all three types of space-time intervals between two events in space-times of any number of dimensions. We also present some preliminary observations on an alternative measurement procedure that can be applied taking into account the gravitational field of the measuring apparatus, and briefly discuss quantum limitations of measurability in this context.Comment: 17 page

The Effects of Entrepreneurial Orientation and Commitment to Objectives on Performance

The relationship between entrepreneurial orientation (EO) and performance is often moderated by different factors. Specifically, scholars have called for research examining whether commitment to long-term objectives improves EO’s effectiveness, believing that commitment may help firms overcome obstacles associated with EO. In response, we collected survey data from executives in 126 small, high-technology firms, and found that EO and commitment to objectives enhanced sales growth. In addition, the study determined that commitment to objectives was associated with greater increased sales growth of companies high in EO, as compared to those low in EO

Lambda(1520) production in d+Au collisions at RHIC

Recent results of $\Lambda$(1520) resonance production in d+Au collisions at $\sqrt{s_{\rm NN}} =$ 200 GeV are presented and discussed in terms of the evolution and freeze-out conditions of a hot and dense fireball medium. Yields and spectra are compared to results from p+p and Au+Au collisions. The $\Lambda$(1520)/$\Lambda$ ratio in d+Au collisions ratio is consistent with the ratio in p+p collisions. This suggests a short time for elastic interactions between chemical and thermal freeze-out. One can conclude that the interaction volume in d+Au collisions is small.Comment: 4 Pages, 3 figures, conference proceedings Quark Matter 200

Vacuum energy: quantum hydrodynamics vs quantum gravity

We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which in the quantum gravity transforms to the cosmological constant problem. We show that in quantum liquids the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid including the radius of the liquid droplet. In the same manner the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability of the whole quantum vacuum.Comment: 14 pages, no figures, added section on the problem of Higgs mass, version accepted for the special issue of JETP Letter

Rotating magnetic solution in three dimensional Einstein gravity

We obtain the magnetic counterpart of the BTZ solution, i.e., the rotating spacetime of a point source generating a magnetic field in three dimensional Einstein gravity with a negative cosmological constant. The static (non-rotating) magnetic solution was found by Clement, by Hirschmann and Welch and by Cataldo and Salgado. This paper is an extension of their work in order to include (i) angular momentum, (ii) the definition of conserved quantities (this is possible since spacetime is asymptotically anti-de Sitter), (iii) upper bounds for the conserved quantities themselves, and (iv) a new interpretation for the magnetic field source. We show that both the static and rotating magnetic solutions have negative mass and that there is an upper bound for the intensity of the magnetic field source and for the value of the angular momentum. The magnetic field source can be interpreted not as a vortex but as being composed by a system of two symmetric and superposed electric charges, one of the electric charges is at rest and the other is spinning. The rotating magnetic solution reduces to the rotating uncharged BTZ solution when the magnetic field source vanishes.Comment: Latex (uses JHEP3.cls), 12 pages. Published versio

The man who invented descriptive geometry

Gaspar Monž je poznat kao otac moderne nacrtne i diferencijalne geometrije . Godine 1764. angažovan je da izradi detaljan nacrt utvrđenja u svom rodnom gradu i njegov rad je primetio jedan oficir iz vojne škole École Royale du Génie de Mézières. Budući da je nacrt bio jako dobar, metode koje je Monž koristio čuvane su kao vojna tajna dugi niz godina. Godine 1780. Monž je postao član Akademije nauka i učestvovao je u radu Komiteta za tegove i mere, koji je imperijalni merni sistem prevodio u metrički. Gaspar je pomogao u osnivanju škole École Centrale des Travaux Publics (kasnije École Polytechnique) gde je i predavao nacrtnu geometriju. Godine 1798. Napoleon je krenuo u pohod na Egipat i zamolio je čuvenog hemičara Kloda Bertolea da regrutuje istaknute naučnike koji bi mu se pridružili u pohodu. Među njima su bili Furije, Monž, Dolomju i Malu. Napoleon je osnovao Egipatski institut i Monž je bio njegov prvi direktor. Gaspar Monž je preminuo 28. jula 1818. godine u Parizu. Njegovo ime je urezano u temelj Ajfelovog tornja i to na mestu tačno preko puta Vojne akademije. Pored nacrtne geometrije, Monž se bavio hemijom i fizikom.Gaspard Monge is known as the father of modern descriptive and differential geometry. In 1764, he was engaged to draw a detailed plan of a fortification in his hometown, which was seen by an officer at the École Royale du Génie de Mézières. This plan was a success and his techniques were marked as a military secret for a long period of time. In 1780, he was elected to the Academy of Science and participated in the work of the Commission for Weights and Measures, that was in charge of moving the system from imperial to metric. In 1794, Monge helped setting up the École Centrale des Travaux Publics (later École Polytechnique) where he was lecturing Descriptive Geometry. In 1798, Napoleon undertook a campaign in Egypt. The famous chemist Claude Louis Berthollet was asked to recruit prominent scientists. Among them were Fourier, Monge, Dolomieu and Malus. Institut d'Egypte was established by Napoleon and Monge was named as its first president. Monge passed away on July 28, 1818. His name is inscribed on the base of the Eiffel Tower and it is located on the third façade opposite the Military Academy. Besides descriptive geometry, he carried on many different researches in chemistry and physics

The man who invented descriptive geometry

Gaspar Monž je poznat kao otac moderne nacrtne i diferencijalne geometrije . Godine 1764. angažovan je da izradi detaljan nacrt utvrđenja u svom rodnom gradu i njegov rad je primetio jedan oficir iz vojne škole École Royale du Génie de Mézières. Budući da je nacrt bio jako dobar, metode koje je Monž koristio čuvane su kao vojna tajna dugi niz godina. Godine 1780. Monž je postao član Akademije nauka i učestvovao je u radu Komiteta za tegove i mere, koji je imperijalni merni sistem prevodio u metrički. Gaspar je pomogao u osnivanju škole École Centrale des Travaux Publics (kasnije École Polytechnique) gde je i predavao nacrtnu geometriju. Godine 1798. Napoleon je krenuo u pohod na Egipat i zamolio je čuvenog hemičara Kloda Bertolea da regrutuje istaknute naučnike koji bi mu se pridružili u pohodu. Među njima su bili Furije, Monž, Dolomju i Malu. Napoleon je osnovao Egipatski institut i Monž je bio njegov prvi direktor. Gaspar Monž je preminuo 28. jula 1818. godine u Parizu. Njegovo ime je urezano u temelj Ajfelovog tornja i to na mestu tačno preko puta Vojne akademije. Pored nacrtne geometrije, Monž se bavio hemijom i fizikom.Gaspard Monge is known as the father of modern descriptive and differential geometry. In 1764, he was engaged to draw a detailed plan of a fortification in his hometown, which was seen by an officer at the École Royale du Génie de Mézières. This plan was a success and his techniques were marked as a military secret for a long period of time. In 1780, he was elected to the Academy of Science and participated in the work of the Commission for Weights and Measures, that was in charge of moving the system from imperial to metric. In 1794, Monge helped setting up the École Centrale des Travaux Publics (later École Polytechnique) where he was lecturing Descriptive Geometry. In 1798, Napoleon undertook a campaign in Egypt. The famous chemist Claude Louis Berthollet was asked to recruit prominent scientists. Among them were Fourier, Monge, Dolomieu and Malus. Institut d'Egypte was established by Napoleon and Monge was named as its first president. Monge passed away on July 28, 1818. His name is inscribed on the base of the Eiffel Tower and it is located on the third façade opposite the Military Academy. Besides descriptive geometry, he carried on many different researches in chemistry and physics

SL(2,R) model with two Hamiltonian constraints

We describe a simple dynamical model characterized by the presence of two noncommuting Hamiltonian constraints. This feature mimics the constraint structure of general relativity, where there is one Hamiltonian constraint associated with each space point. We solve the classical and quantum dynamics of the model, which turns out to be governed by an SL(2,R) gauge symmetry, local in time. In classical theory, we solve the equations of motion, find a SO(2,2) algebra of Dirac observables, find the gauge transformations for the Lagrangian and canonical variables and for the Lagrange multipliers. In quantum theory, we find the physical states, the quantum observables, and the physical inner product, which is determined by the reality conditions. In addition, we construct the classical and quantum evolving constants of the system. The model illustrates how to describe physical gauge-invariant relative evolution when coordinate time evolution is a gauge.Comment: 9 pages, 1 figure, revised version, to appear in Phys. Rev.