- #1,716
John86
- 257
- 9
http://arxiv.org/abs/1205.1296
A Distinguished Vacuum State for a Quantum Field in a Curved Spacetime: Formalism, Features, and Cosmology
Niayesh Afshordi, Siavash Aslanbeigi, Rafael D. Sorkin
(Submitted on 7 May 2012)
We define a distinguished "ground state" or "vacuum" for a free scalar quantum field in a globally hyperbolic region of an arbitrarily curved spacetime. Our prescription is motivated by the recent construction of a quantum field theory on a background causal set using only knowledge of the retarded Green's function. We generalize that construction to continuum spacetimes and find that it yields a distinguished vacuum or ground state for a non-interacting, massive or massless scalar field. This state is defined for all compact regions and for many noncompact ones. In a static spacetime we find that our vacuum coincides with the usual ground state. We determine it also for a radiation-filled, spatially homogeneous and isotropic cosmos, and show that the super-horizon correlations are approximately the same as those of a thermal state. Finally, we illustrate the inherent non-locality of our prescription with the example of a spacetime which sandwiches a region with curvature in-between flat initial and final regions.
http://arxiv.org/abs/1205.1308[
Testing MOND over a large acceleration range in x-ray ellipticals
Mordehai Milgrom
(Submitted on 7 May 2012)
The gravitational fields of two isolated ellipticals, NGC 720 and NGC 1521, have been recently measured, assuming hydrostatic balance of the hot gas enshrouding them. These galaxies are worthy of special interest: They afford, for the first time to my knowledge, testing MOND in ellipticals with force and quality that, arguably, approach those of rotation-curve tests in disc galaxies: The fields have been probed to very large galactic radii, revealing a large range of mass discrepancies. In the context of MOND, it is noteworthy that the measured accelerations span a wide range, from more than 10a0 to about a0/10, unprecedented in individual ellipticals. I compare the predictions of MOND, based on only the baryonic mass, for reasonable stellar M/L values, with the deduced dynamical mass runs of these galaxies. I find that MOND predicts correctly the runs of the mass discrepancies: from no discrepancy in the inner parts, to approximately a-factor-of-ten discrepancy in the outermost regions probed. For NGC 1521, this is achieved with the same M/L value as best fitted the data in the Newtonian analysis with dark matter, and for NGC 720, with a somewhat larger value than preferred by the Newtonian fit.
http://arxiv.org/abs/1205.1317
A novel MOND effect in isolated high acceleration systems
Mordehai Milgrom
(Submitted on 7 May 2012)
I discuss a novel MOND effect that entails a small correction to the dynamics of isolated mass systems even when they are deep in the Newtonian regime. [These are systems whose extent R<< Rm, where Rm=sqrt(GM/a0) is the MOND radius of the system, of total mass M.] Interestingly, even if the MOND equations approach Newtonian dynamics arbitrarily fast at high accelerations, this correction decreases only as a power of R/Rm. The effect appears in formulations of MOND as modified gravity governed by generalizations of the Poisson equation. The MOND correction to the potential is a quadrupole field \phi_{a} \approx GP_{ij}r^ir^j, where r is the radius from the center of mass. In QUMOND, P_{ij}=-q Q_{ij}/Rm^5, where Q_{ij} is the quadrupole moment of the system, and q>0 is a numerical factor that depends on the interpolating function. For example, the correction to the Newtonian force between two masses, m and M, a distance L apart (L<<Rm) is Fa=2q(L/Rm)^3(mM)^2(M+m)^{-3}a0 (attractive). At present I don't see where this effect can be tested. For example, it's predicted strength is rather much below present testing capabilities in the solar system, for which the added acceleration is of order 10^{-12}a0. (Abridged)
http://arxiv.org/abs/1205.1439
Are quantum states real?
Lucien Hardy
(Submitted on 7 May 2012 (v1), last revised 8 May 2012 (this version, v2))
In this paper we give a new argument for the reality of the wavefunction. We consider theories in which reality is described by some underlying variables. Each value of these variables can take represents an ontic state (a particular state of reality). The preparation of a quantum state corresponds to a distribution over the ontic states. Using three basic assumptions, we will show that the distributions over ontic states corresponding to distinct pure states are non-overlapping. This means that we can deduce the quantum state from a knowledge of the ontic state. Hence we can claim that the quantum state is a real thing (it is written into the underlying variables that describe reality). The key assumption we use in this proof is ontic indifference - that quantum transformations that do not effect a given pure quantum state can be implemented in such a way that they do not effect the ontic states in the support of that state. This argument in this paper is different from the recent proof of Pusey, Barrett, and Rudolph. It uses a different key assumption and it pertains to a single copy of the system in question.
http://arxiv.org/abs/1205.1584
Everything is Entangled
Roman V. Buniy, Stephen D.H. Hsu
(Submitted on 8 May 2012)
We show that big bang cosmology implies a high degree of entanglement of particles in the universe. In fact, a typical particle is entangled with many particles far outside our horizon. However, the entanglement is spread nearly uniformly so that two randomly chosen particles are unlikely to be directly entangled with each other -- the reduced density matrix describing any pair is likely to be separable.
http://arxiv.org/abs/1205.1619
Quantum Theory as emergent from an undulatory translocal Sub-Quantum Level
Manfred Requardt
(Submitted on 8 May 2012)
We argue that quantum theory is a low-energy effective theory which emerges from some sub-quantum level theory which is of an undulatory and translocal character. We show the close connection of quantum theory with both gravity and the holographic principle which are different phenomena of one and the same theory on this primordial level. An important role in our analysis is played by the concept of a generalized renormalization group connecting this primordial level and e.g. quantum theory plus a continuous space-time. We show that characteristic phenomena like the seemingly instantaneous state reduction, the EPR-paradox or the problem of polydimensions can be understood in our undulatory translocal theory in a realistic way. Most importantly, we give a realistic interpretation of the phasefunction as a collective action variable in the spirit of Bohm and explain the emergence of a macroscopic notion of time.