Vacuum driven accelerated expansion

It has been shown that an improved estimation of quantum vacuum energy can yield not only acceptable but also experimentally sensible results. The very idea consists in a straightforward extraction of gravitationally interacting part of the full quantum vacuum energy by means of gauge transformations. The implementation of the idea has been performed in the formalism of effective action, in the language of Schwinger's proper time and the Seeley-DeWitt heat kernel expansion, in the background of the Friedmann-Robertson-Walker geometry.Comment: 11 pages, 2 figures, minor improvements, final preprint version, published version: http://www3.interscience.wiley.com/journal/120847180/abstract, devoted to the memory of professor Ryszard Raczka on the occasion of the 11th anniversary of his deat

Analysis of the possibility of analog detectors calibration by exploiting Stimulated Parametric Down Conversion

Spontaneous parametric down conversion (SPDC) has been largely exploited as a tool for absolute calibration of photon-counting detectors, i.e detectors registering very small photon fluxes. In [J. Opt. Soc. Am. B 23, 2185 (2006)] we derived a method for absolute calibration of analog detectors using SPDC emission at higher photon fluxes, where the beam is seen as a continuum by the detector. Nevertheless intrinsic limitations appear when high-gain regime of SPDC is required to reach even larger photon fluxes. Here we show that stimulated parametric down conversion allow one to avoid this limitation, since stimulated photon fluxes are increased by the presence of the seed beam.Comment: 9 pages, 1 figur

Bone Marrow Donor Recruitment Drive and Registry

Bone marrow transplants are vital for those with blood cancers and disorders, but not every ethnic group has an equal chance of finding a match. Some of the human leukocyte antigen (HLA) cell markers used to match donors and recipients are unique to certain ethnic groups, making it harder for members of those groups to find a match. This project worked to address this inequality by organizing a bone marrow registry recruitment drive on the campus of Andrews University in partnership with the NMDP registry. It encompassed the planning, promotion, and execution of the drive which took place March 5-7, 2024. The project garnered more than 96 completed and in-progress registrations for the registry

Moment instabilities in multidimensional systems with noise

We present a systematic study of moment evolution in multidimensional stochastic difference systems, focusing on characterizing systems whose low-order moments diverge in the neighborhood of a stable fixed point. We consider systems with a simple, dominant eigenvalue and stationary, white noise. When the noise is small, we obtain general expressions for the approximate asymptotic distribution and moment Lyapunov exponents. In the case of larger noise, the second moment is calculated using a different approach, which gives an exact result for some types of noise. We analyze the dependence of the moments on the system's dimension, relevant system properties, the form of the noise, and the magnitude of the noise. We determine a critical value for noise strength, as a function of the unperturbed system's convergence rate, above which the second moment diverges and large fluctuations are likely. Analytical results are validated by numerical simulations. We show that our results cannot be extended to the continuous time limit except in certain special cases.Comment: 21 pages, 15 figure

Digital Media Technology and Your Spiritual Life: An Uneasy Alliance

Digital media technology has become a part of our everyday lives, filling a substantial portion of the constructive minutes and hours of our days. This technology was created by engineers, and is being further perfected by engineers with each successive generation. As engineers, should we not be at the forefront of learning how this technology is changing our culture and be leaders in teaching responsible use? Science has documented that technology use is changing how our brain functions. Its use creates new neural pathways and causes cognitive overload in the area of our brain that controls decision-making, impulse control, attention, focus and short-term memory – reducing those functions. Our digital media technology use encourages bad habits that affect our focus, productivity, busyness, reading skills and our personal interactions. These changes in our brain processing also affect our spiritual life. Their distracting nature affects spiritual meditation, prayer and contemplation. The changes in our reading habits affect our study of Scripture, and storing God’s word in our hearts. Changes in how we interact with each other affect worship and fellowship, as well as how we relate to God. Most people have wandered into using digital media technology without a conscious realization of how it is changing their lives and the function of their brain. As engineers, creators of technology, let’s lead the charge in educating ourselves to build protective walls around our spiritual lives, and educating others to do the same

Design in Nature: Observing and Voicing God’s Glory within an Engineering Vocation

“In the beginning, God created the heavens and the earth.” [Gen. 1:1] The Bible starts with the most colossal, grandiose and formidable engineering feat ever. Without debating the literacy of the account, the Genesis creation story presents a prudent engineering critical path flowchart for filling the earth – making sure all the biological needs of each species are in place before it is called into being, and placement in a setting where arbitrary and unrelated constants of physics are amazingly and inscrutably fine-tuned to the narrow, precise values needed to sustain life. [1] The complexities of the process of creation and its life-sustaining environment is a dramatic engineering feat, much less the intricacy of design embedded in each individual plant, animal, insect, bird or fish. Our universe has all the fingerprints of a designer, whether you look with the naked eye, with a high-powered telescope or a high-powered microscope - from the far-flung galaxies to the microscopic details. By observing how specific and exact the interworking’s of creation are, its intricacies and precision, one can concede that there must be a Designer. This is acknowledged even by the secular world. Albert Einstein, though not a believer, expressed “I’m not an atheist. The problem involved is too vast for our limited minds. … We see the universe marvelously arranged and obeying certain laws but only dimly understand these laws.” [2] An agnostic Cambridge University astrophysicist, Fred Hoyle, upon realizing a how narrowly precise a physical parameter had to be to support life, concluded “A common sense interpretation of the facts suggests that a super-intellect has monkeyed with physics, as well as with chemistry and biology, and there are no blind forces worth speaking about in nature.” [3] As Christians, the forethought and design found in the created world points us directly to God. John Glenn, observing the heavens and the earth from his spacecraft window exclaimed To look out at this kind of creation and not believe in God is to me impossible. It just strengthens my faith.” [4] The Bible tells us that God is revealed in the created world. “For [God’s] invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made.” [Romans 1:20 ESV] C.S. Lewis, the legendary scholar and Christian apologist, devoted several pages of his book The Four Loves to the Christian’s relationship with nature. [5] He points out that nature also gives language and meaning to our faith. “Many people – I am one myself – would never, but for what nature does to us, have any content to put into the words we must use in confessing our faith. … If nature had never awakened certain longings in me, huge areas of what I can now mean by the “love” of God would never, so far as I can see, have existed.” The mystery and awe of nature can be a deeply spiritual, emotional experience that evokes divine worship, similar to profoundly moving music, and causes us to recognize and extol the goodness and glory of God. The natural world is a reflection of God’s glory and gives “content to put into the words we must use in confessing our faith.

Nonlinear evolution of dark matter and dark energy in the Chaplygin-gas cosmology

The hypothesis that dark matter and dark energy are unified through the Chaplygin gas is reexamined. Using generalizations of the spherical model which incorporate effects of the acoustic horizon we show that an initially perturbative Chaplygin gas evolves into a mixed system containing cold dark matter-like gravitational condensate.Comment: 11 pages, 3 figures, substantial revision, title changed, content changed, added references, to appear in JCA

Measuring the Cosmic Web

A quantitative study of the clustering properties of the cosmic web as a function of absolute magnitude and colour is presented using the SDSS Data Release 7 galaxy survey. Mark correlations are included in the analysis. We compare our results with mock galaxy samples obtained with four different semi-analytical models of galaxy formation imposed on the merger trees of the Millenium simulation. The clustering of both red and blue galaxies is studied separately.Comment: 8 pages, 5 figures, to be published in Baltic Astronom

Dynamics of a thin shell in the Reissner-Nordstrom metric

We describe the dynamics of a thin spherically symmetric gravitating shell in the Reissner-Nordstrom metric of the electrically charged black hole. The energy-momentum tensor of electrically neutral shell is modelled by the perfect fluid with a polytropic equation of state. The motion of a shell is described fully analytically in the particular case of the dust equation of state. We construct the Carter-Penrose diagrams for the global geometry of the eternal black hole, which illustrate all possible types of solutions for moving shell. It is shown that for some specific range of initial parameters there are possible the stable oscillating motion of the shell transferring it consecutively in infinite series of internal universes. We demonstrate also that this oscillating type of motion is possible for an arbitrary polytropic equation of state on the shell.Comment: 17 pages, 7 figure