Scientists propose test of string theory based on neutral hydrogen absorption

Ancient light absorbed by neutral hydrogen atoms could be used to test certain predictions of string theory, say cosmologists at the University of Illinois. Making the measurements, however, would require a gigantic array of radio telescopes to be built on Earth, in space or on the moon. String theory – a theory whose fundamental building blocks are tiny one-dimensional filaments called strings – is the leading contender for a “theory of everything.” Such a theory would unify all four fundamental forces of nature (the strong and weak nuclear forces, electromagnetism, and gravity). But finding ways to test string theory has been difficult. Now, cosmologists at the U. of I. say absorption features in the 21-centimeter spectrum of neutral hydrogen atoms could be used for such a test. “High-redshift, 21-centimeter observations provide a rare observational window in which to test string theory, constrain its parameters and show whether or not it makes sense to embed a type of inflation – called brane inflation – into string theory,” said Benjamin Wandelt, a professor of physics and of astronomy at the U. of I.“If we embed brane inflation into string theory, a network of cosmic strings is predicted to form,” Wandelt said. “We can test this prediction by looking for the impact this cosmic string network would have on the density of neutral hydrogen in the universe.” Wandelt and graduate student Rishi Khatri describe their proposed test in a paper accepted for publication in the journal Physical Review Letters.About 400,000 years after the Big Bang, the universe consisted of a thick shell of neutral hydrogen atoms (each composed of a single proton orbited by a single electron) illuminated by what became known as the cosmic microwave background.
Because neutral hydrogen atoms readily absorb electromagnetic radiation with a wavelength of 21 centimeters, the cosmic microwave background carries a signature of density perturbations in the hydrogen shell, which should be observable today, Wandelt said. Cosmic strings are filaments of infinite length. Their composition can be loosely compared to the boundaries of ice crystals in frozen water. When water in a bowl begins to freeze, ice crystals will grow at different points in the bowl, with random orientations. When the ice crystals meet, they usually will not be aligned to one another. The boundary between two such misaligned crystals is called a discontinuity or a defect. Cosmic strings are defects in space. A network of strings is predicted by string theory (and also by other supersymmetric theories known as Grand Unified Theories, which aspire to unify all known forces of nature except gravity) to have been produced in the early universe, but has not been detected so far.
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Bulas’ Particles break the universe down

Bulas was fascinated with mysterious charts and figures of quantum mechanics and satellite images of the farthest reaches of the universe. At first, he just looked at the pictures: the intricacy of the lines, the Rembrantesque light of outer space, the spectacular collisions of galaxies. It was these images more than any painting that gave him inspiration for his art. But gradually Bulas began to read the inscriptions below the images. He then realized that the world of astrophysics that he had just entered was stranger than science fiction. It was a world that transported him to a universe beyond our imagination: where stars like Arcturus flew towards us at two miles a second and where our entire solar system appears as a speck of dust. On the microscopic scale things got even weirder; here a colliding atom once split (in a process called quantum entanglement) could affect an atom thousands of miles away. Science, the bastion of reason, layered mystery upon mystery and uncovered more questions than answers. By now Bulas was captivated. From now on his art turned this new science into poetry. Bulas began his prints by surrounding himself with anything from models of valence electrons, to photos of plasma jets, to atomic dust halos. Then—working from several images at once—he crafted each print for hours using the oldest and most labourious printmaking techniques. To him it became a type of meditation: the stellar dust, distant galaxies that emerged from under his hands became intimate, private subjects of contemplation.

Scientists may hold key to a cosmic enigma: study

Astrophysicists believe they are closing in on one of the cosmos' great mysteries: why the expansion of the Universe, triggered by the Big Bang, is accelerating.
The answer could be tantalisingly within reach, according to their study, released on Wednesday by the British weekly science journal Nature.A decade ago, astronomers were stunned to learn that the Universe was expanding more quickly than in the past.It had long been assumed that the mutual attraction of galaxies through gravity would slow the expansion of space, kicked off by the Big Bang some 14 billion years ago. Two very different theories have emerged to explain this shock discovery. One is that the Universe is filled with so-called dark energy, a substance that has been inferred but never seen. Dark energy cannot be detected with present technology as it neither emits nor reflects light or radiation. Dark energy, so the theory goes, counteracts the gravitational attraction that galaxies exert on each other and which would otherwise brake the cosmic expansion. The other possible explanation is that dark energy does not exist. If this were true, current theories about gravitational force as the prime mover in the Universe would be flawed -- they would only make sense if there are additional dimensions to space.

Finding a door to a parallel universe.

If there were a portal linking us to a parallel universe or some other region of space, how would we spot it? One suggestion is that it will give itself away by the curious way it bends light.
The existence of wormholes linking different regions of space was suggested in 1916 by the Austrian physicist Ludwig Flamm as a possible solution to equations of general relativity, which Einstein had published that year. They have since become accepted as a natural consequence of general relativity, which predicts that matter entering one end of a wormhole would instantly emerge somewhere else, so long as the wormhole is somehow propped open.
Though no direct evidence for wormholes has been observed, this could be because they are disguised as black holes. Now Alexander Shatskiy of the Lebedev Physical Institute in Moscow, Russia, is suggesting a possible way to tell the two kinds of object apart. His idea assumes the existence of a bizarre substance called “phantom matter”, which has been proposed to explain how wormholes might stay open. Phantom matter has negative energy and negative mass, so it creates a repulsive effect that prevents the wormhole closing.