On a common misunderstanding of the Birkhoff theorem and light deflection calculation: generalized Shapiro delay and its possible laboratory test

In Newtonian gravity (NG) it is known that the gravitational field anywhere inside a spherically symmetric distribution of mass is determined only by the enclosed mass. This is also widely believed to be true in general relativity (GR), and the Birkhoff theorem is often invoked to support this analogy between NG and GR. Here we show that such an understanding of the Birkhoff theorem is incorrect and leads to erroneous calculations of light deflection and delay time through matter. The correct metric, matching continuously to the location of an external observer, is determined both by the enclosed mass and mass distribution outside. The effect of the outside mass is to make the interior clock run slower, i.e., a slower speed of light for external observer. We also discuss the relations and differences between NG and GR, in light of the results we obtained in this Lettework. Finally we discuss the Generalized Shapiro delay, caused by the outside mass, and its possible laboratory test.Comment: 12 pages, 4 figures, invited talk in the 2nd Galileo-Xu Guangqi Meeing, Italy, 2011, IJMPD in pres

Entropy of Contracting Universe in Cyclic Cosmology

Following up a recent proposal \cite{BF} for a cyclic model based on phantom dark energy, we examine the content of the contracting universe (cu) and its entropy $S_{cu}$. We find that beyond dark energy the universe contains on average zero or at most a single photon which if present immediately after turnaround has infinitesimally energy which subsequently blue shifts to produce $e^+e^-$ pairs. These statements are independent of the equation of state $\omega = p/\rho$ of dark energy provided $\omega < -1$. Thus $S_{cu} = 0$ and if observations confirm $\omega < -1$ the entropy problem is solved. We discuss the absence of a theoretical lower bound on $\phi = |\omega + 1|$, then describe an anthropic fine tuning argument that renders unlikely extremely small $\phi$. The present bound $\phi \lesssim 0.1$ already implies a time until turnaround of $(t_T - t_0) \gtrsim 100$ Gy.Comment: 5 pages late

Cyclic Universe and Infinite Past

We address two questions about the past for infinitely cyclic cosmology. The first is whether it can contain an infinite length null geodesic into the past in view of the Borde-Guth-Vilenkin (BGV) "no-go" theorem, The second is whether, given that a small fraction of spawned universes fail to cycle, there is an adequate probability for a successful universe after an infinite time. We give positive answers to both questions then show that in infinite cyclicity the total number of universes has been infinite for an arbitrarily long time.Comment: 7 pages. Clarification in discussion of infinite pas

Investigation of multilayer magnetic domain lattice file

A theoretical and experimental investigation determined that current accessed self structured bubble memory devices have the potential of meeting projected data density and speed requirements. Device concepts analyzed include multilayer ferrimagnetic devices where the top layer contains a domain structure which defines the data location and the second contains the data. Current aperture and permalloy assisted current propagation devices were evaluated. Based on the result of this work more detailed device research was initiated. Detailed theoretical and experimental studies indicate that the difference in strip and threshold between a single bubble in the control layer and a double bubble which would exist in both the control layer and data layer is adequate to allow for detection of data. Detailed detector designs were investigated

Investigation of multilayer magnetic domain lattice file

The feasibility of the self structured multilayered bubble domain memory as a mass memory medium for satellite applications is examined. Theoretical considerations of multilayer bubble supporting materials are presented, in addition to the experimental evaluation of current accessed circuitry for various memory functions. The design, fabrication, and test of four device designs is described, and a recommended memory storage area configuration is presented. Memory functions which were demonstrated include the current accessed propagation of bubble domains and stripe domains, pinning of stripe domain ends, generation of single and double bubbles, generation of arrays of coexisting strip and bubble domains in a single garnet layer, and demonstration of different values of the strip out field for single and double bubbles indicating adequate margins for data detection. All functions necessary to develop a multilayer self structured bubble memory device were demonstrated in individual experiments

The spherical symmetry Black hole collapse in expanding universe

The spherical symmetry Black holes are considered in expanding background. The singularity line and the marginally trapped tube surface behavior are discussed. In particular, we address the conditions whether dynamical horizon forms for these cosmological black holes. We also discuss about the cosmological constant effect on these black hole and the redshift of the light which comes from the marginally trapped tube surface.Comment: 7 pages, 3 figures. Accepted for publication in International Journal of Modern Physics D (IJMPD). arXiv admin note: text overlap with arXiv:gr-qc/0308033 and arXiv:gr-qc/030611

The Hawking temperature of expanding cosmological black holes

In the context of a debate on the correct expression of the Hawking temperature of an expanding cosmological black hole, we show that the correct expression in terms of the Hawking-Hayward quasi-local energy m of the hole is T=1/(8\pi m(t)). This expression holds for comoving black holes and agrees with a recent proposal by Saida, Harada, and Maeda.Comment: 5 latex pages, to appear in Phys. Rev. D. Some references adde

Planck Fluctuations, Measurement Uncertainties and the Holographic Principle

Starting from a critical analysis of recently reported surprisingly large uncertainties in length and position measurements deduced within the framework of quantum gravity, we embark on an investigation both of the correlation structure of Planck scale fluctuations and the role the holographic hypothesis is possibly playing in this context. While we prove the logical independence of the fluctuation results and the holographic hypothesis (in contrast to some recent statements in that direction) we show that by combining these two topics one can draw quite strong and interesting conclusions about the fluctuation structure and the microscopic dynamics on the Planck scale. We further argue that these findings point to a possibly new and generalized form of quantum statistical mechanics of strongly (anti)correlated systems of degrees of freedom in this fundamental regime.Comment: 19 pages, Latex, no figures, some new references, to appear ModPhysLett

Failure of the work-Hamiltonian connection for free energy calculations

Extensions of statistical mechanics are routinely being used to infer free energies from the work performed over single-molecule nonequilibrium trajectories. A key element of this approach is the ubiquitous expression dW/dt=\partial H(x,t)/ \partial t which connects the microscopic work W performed by a time-dependent force on the coordinate x with the corresponding Hamiltonian H(x,t) at time t. Here we show that this connection, as pivotal as it is, cannot be used to estimate free energy changes. We discuss the implications of this result for single-molecule experiments and atomistic molecular simulations and point out possible avenues to overcome these limitations

Alternative Methods of Describing Structure Formation in the Lemaitre-Tolman Model

We describe several new ways of specifying the behaviour of Lemaitre-Tolman (LT) models, in each case presenting the method for obtaining the LT arbitrary functions from the given data, and the conditions for existence of such solutions. In addition to our previously considered `boundary conditions', the new ones include: a simultaneous big bang, a homogeneous density or velocity distribution in the asymptotic future, a simultaneous big crunch, a simultaneous time of maximal expansion, a chosen density or velocity distribution in the asymptotic future, only growing or only decaying fluctuations. Since these conditions are combined in pairs to specify a particular model, this considerably increases the possible ways of designing LT models with desired properties.Comment: Accepted by Phys Rev D. RevTeX 4, 13 pages, no figures. Part of a series: gr-qc/0106096, gr-qc/0303016, gr-qc/0309119. Replacement contains very minor correction