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Asteroid Diversity: Mixed Bag of Space Rocks Found Near Earth

Posted: September 2nd, 2010, 6:03am PDT

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A new survey of asteroids near Earth shows these space rocks are a mixed bag, with some shiny and bright, others dark and dull.

Starburst Galaxy Unleashes Gassy 'Superwind'

Posted: September 2nd, 2010, 6:03am PDT

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A striking galaxy buzzing with energetic star formation takes center stage in a new photograph that showcases an unusual "superwind" of out-flowing gas.

Hurricane Earl Photographed From Space by Astronaut

Posted: September 2nd, 2010, 6:03am PDT

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A space station astronaut has photographed Hurricane Earl as it heads towards the U.S. coast as a powerful Category 4 storm.

NASA Aims to Plunge Car-Sized Probe Into the Sun

Posted: September 2nd, 2010, 6:03am PDT

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NASA is developing a mission to plunge a car-sized probe directly into the sun's atmosphere, exploring a region no spacecraft has ever visited.

Hawking: God Didn't Create the Universe

Posted: September 2nd, 2010, 6:03am PDT

Labor Day Weekend for Astronauts: Space Toilet Cleaning and Exercise

Posted: September 2nd, 2010, 6:03am PDT

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The astronauts aboard the International Space Station won't be throwing any burgers on the grill this Labor Day, but at least they'll get the holiday off.

Supernova Blast Wave Could Shape Galaxy Evolution

Posted: September 2nd, 2010, 6:03am PDT

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A new glimpse of a well-known supernova could provide new clues about how dying stars affect their surroundings.

Airbag Designer Casts Eye on NASA's Escape Ship

Posted: September 2nd, 2010, 6:03am PDT

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New airbag technology that mimics nature's way of protecting seed embryos could take the bumps out of spacecraft landings.

On Months-Long Missions, How Durable Is An Astronaut's Mind?

Posted: September 2nd, 2010, 6:03am PDT

Volunteers in Russia are approaching the three-month mark in their record 520-day Mars spaceflight simulation. Meanwhile, researchers will continue to pay close attention to how the six volunteer "astronauts" physically and psychologically cope throughout the mock mission to the red planet.

Group of Navigation Satellites Launched by Proton Rocket

Posted: September 2nd, 2010, 6:03am PDT

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A Proton rocket launched Wednesday bearing three spacecraft to help expand Russia's satellite navigation system.

Solar Sail Spacecraft Could Explore Beyond Solar System

Posted: September 2nd, 2010, 6:03am PDT

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Sun-powered spacecraft could be the ticket to traveling beyond the solar system, scientists say.

Space Luminaries Petition Against House Version of NASA Bill

Posted: September 2nd, 2010, 6:03am PDT

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In a new letter 30 Nobel laureates and space officials argue for different NASA spending priorities in a bill working through Congress.

TV's 'Top Chefs' Cook Up Ultimate Astronaut Takeout

Posted: September 2nd, 2010, 6:03am PDT

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NASA is challenging the cooks of TV's 'Top Chef' to dream up a new meal for astronauts.

Europe, Japan Weigh Cargo Return from Space Station

Posted: September 2nd, 2010, 6:03am PDT

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European and Japanese space agencies are considering upgrades to outfit their robotic space station-servicing spacecraft to return cargo to Earth.

Space Shuttle Commander, Spacewalker to Leave NASA

Posted: September 2nd, 2010, 6:03am PDT

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Veteran astronauts Linda Godwin and Scott Altman are leaving NASA, the space agency announced Tuesday.

Old Star's Super-Hot Water Vapor Surprises Scientists

Posted: September 2nd, 2010, 6:03am PDT

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Hot water vapor has been discovered in the atmosphere of an aging star, surprising scientists who thought the chemistry of such stars would have forbid it.

LiveScience: NASA: Food, Emotional Support Vital for Trapped Chile Miners

Posted: September 2nd, 2010, 6:03am PDT

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For Star-Gazers, September Brings New Night Sky

Posted: September 2nd, 2010, 6:03am PDT

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September brings a new view of the night sky as the autumn constellations appear.

Hubble Telescope Engineer Pulls Double Duty As Real-Life Knight

Posted: September 2nd, 2010, 6:03am PDT

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A Hubble engineer, and a native of the Dutch island of Aruba, has received the highest civilian order in the Netherlands.

Big Alien Planet's Weather Forecast: Hot and Extra Cloudy

Posted: September 2nd, 2010, 6:03am PDT

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Astronomers peering at a gas-giant exoplanet found it has an atmosphere unlike that of any extrasolar planet yet studied.

Nonperturbative Results for Yang-Mills Theories. (arXiv:1009.0265v1 [hep-ph])

Fetched: September 2nd, 2010, 5:45am PDT by Francesco Sannino (CP3-Origins), Joseph Schechter (Syracuse University)

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Some non perturbative aspects of the pure SU(3) Yang-Mills theory are investigated assuming a specific form of the beta function, based on a recent modification by Ryttov and Sannino of the known one for supersymmetric gauge theories. The characteristic feature is a pole at a particular value of the coupling constant, g. First it is noted, using dimensional analysis, that physical quantities behave smoothly as one travels from one side of the pole to the other. Then it is argued that the form of the integrated beta function g(m), where m is the mass scale, determines the mass gap of the theory. Assuming the usual QCD value one finds it to be 1.67 GeV, which is in surprisingly good agreement with a quenched lattice calculation. A similar calculation is made for the supersymmetric Yang-Mills theory where the corresponding beta function is considered to be exact.

Stability of spin-0 graviton and strong coupling in Horava-Lifshitz theory of gravity. (arXiv:1009.0268v1 [hep-th])

Fetched: September 2nd, 2010, 5:45am PDT by Anzhong Wang, Qiang Wu

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In this paper, we consider two different issues, stability and strong coupling, raised lately in the newly-proposed Horava-Lifshitz (HL) theory of quantum gravity with projectability condition. We find that all the scalar modes are stable in the de Sitter background, due to two different kinds of effects, one from high-order derivatives of the spacetime curvature, and the other from the exponential expansion of the de Sitter space. Combining these effects properly, one can make the instability found in the Minkowski background never raise even for small-scale modes, provided that the IR limit is sufficiently closed to the relativistic fixed point. At the fixed point, all the modes become stabilized, which is expected, as it is well-known that the de Sitter spacetime is stable in general relativity. We also show that the instability of Minkowski spacetime can be cured by introducing mass to the spin-0 graviton. The strong coupling problem is investigated following the effective field theory approach, and found that it cannot be cured by the Blas-Pujolas-Sibiryakov mechanism, initially designed for the case without projectability condition, but might be solved by the Vainshtein mechanism. In fact, we construct a class of non-perturbative solutions, and show explicitly that it reduces smoothly to the de Sitter spacetime in the relativistic limit.

What is a sequence of Nilsson type?. (arXiv:1009.0276v1 [math.GT])

Fetched: September 2nd, 2010, 5:45am PDT by Stavros Garoufalidis

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Sequences of Nilsson type appear in abundance in Algebraic Geometry, Enumerative Combinatorics, Mathematical Physics and Quantum Topology. We give an elementary introduction on this subject, including the definition of sequences of Nilsson type and the uniqueness, existence, and effective computation of their asymptotic expansion.

N=2 S-duality via Outer-automorphism Twists. (arXiv:1009.0339v1 [hep-th])

Fetched: September 2nd, 2010, 5:45am PDT by Yuji Tachikawa

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Compactification of 6d N=(2,0) theory of type G on a punctured Riemann surface has been effectively used to understand S-dualities of 4d N=2 theories. We can further introduce branch cuts on the Riemann surface across which the worldvolume fields are transformed by the discrete symmetries associated to those of the Dynkin diagram of type G. This allows us to generate more S-dualities, and in particular to reproduce a couple of S-dual pairs found previously by Argyres and Wittig.

AGT on the S-duality Wall. (arXiv:1009.0340v1 [hep-th])

Fetched: September 2nd, 2010, 5:45am PDT by Kazuo Hosomichi, Sungjay Lee, Jaemo Park

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Three-dimensional gauge theory T[G] arises on a domain wall between four-dimensional N=4 SYM theories with the gauge groups G and its S-dual G^L. We argue that the N=2^* mass deformation of the bulk theory induces a mass-deformation of the theory T[G] on the wall. The partition functions of the theory T[SU(2)] and its mass-deformation on the three-sphere are shown to coincide with the transformation coefficient of Liouville one-point conformal block on torus under the S-duality.

Quantum Gravity Corrections and Entropy at the Planck time. (arXiv:1009.0365v1 [hep-th])

Fetched: September 2nd, 2010, 5:45am PDT by Spyros Basilakos, Saurya Das, Elias C. Vagenas

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We investigate the effects of Quantum Gravity on the Planck era of the universe. In particular, using different versions of the Generalized Uncertainty Principle and under specific conditions we find that the main Planck quantities such as the Planck time, length, mass and energy become larger by a factor of order 10-10^{4} compared to those quantities which result from the Heisenberg Uncertainty Principle. However, we prove that the dimensionless entropy enclosed in the cosmological horizon at the Planck time remains unchanged. These results, though preliminary, indicate that we should anticipate modifications in the set-up of cosmology since changes in the Planck era will be inherited even to the late universe through the framework of Quantum Gravity (or Quantum Field Theory) which utilizes the Planck scale as a fundamental one. More importantly, these corrections will not affect the entropic content of the universe at the Planck time which is a crucial element for one of the basic principles of Quantum Gravity named Holographic Principle.

Contractions of Filippov algebras. (arXiv:1009.0372v1 [math-ph])

Fetched: September 2nd, 2010, 5:45am PDT by J.A. de Azcarraga, J.M. Izquierdo, M. Picon

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We introduce in this paper the contractions $\mathfrak{G}_c$ of $n$-Lie (or Filippov) algebras $\mathfrak{G}$ and show that they have a semidirect structure as their $n=2$ Lie algebra counterparts. As an example, we compute the non-trivial contractions of the simple $A_{n+1}$ Filippov algebras. By using the \.In\"on\"u-Wigner and the generalized Weimar-Woods contractions of ordinary Lie algebras, we compare (in the $\mathfrak{G}=A_{n+1}$ simple case) the Lie algebras Lie$\,\mathfrak{G}_c$ (the Lie algebra of inner endomorphisms of $\mathfrak{G}_c$) with certain contractions $(\mathrm{Lie}\,\mathfrak{G})_{IW}$ and $(\mathrm{Lie}\,\mathfrak{G})_{W-W}$ of the Lie algebra Lie$\,\mathfrak{G}$ associated with $\mathfrak{G}$.

M-flation and its spectators. (arXiv:1009.0421v1 [astro-ph.CO])

Fetched: September 2nd, 2010, 5:45am PDT by Marieke Postma

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M-flation is an implementation of assisted inflation, in which the inflaton fields are three N_c x N_c non-abelian hermitean matrices. The model can be consistently truncated to an effectively single field inflation model, with all ``spectator'' fields fixed at the origin. We show that starting with random initial conditions for all fields the truncated sector is not a late-time attractor, but instead the system evolves towards quadratic assisted inflation with all fields mass degenerate. Demanding the energy density during inflation to be below the effective quantum gravity scale, we find that the number of fields, and thus the assisted effect, is bounded N_c < 10^2.

A numerical algorithm for the explicit calculation of SU(N) and SL(N,C) Clebsch-Gordan coefficients. (arXiv:1009.0437v1 [math-ph])

Fetched: September 2nd, 2010, 5:45am PDT by Arne Alex, Matthias Kalus, Alan Huckleberry, Jan von Delft

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We present an algorithm for the explicit numerical calculation of SU(N) and SL(N,C) Clebsch-Gordan coefficients, based on the Gelfand-Tsetlin pattern calculus. Our algorithm is well-suited for numerical implementation; we include a computer code in an appendix. Our exposition presumes only familiarity with the representation theory of SU(2).

Permalink for 'On unitarity of a linearized Yang-Mills formulation for massless and massive gravity with propagating torsion. (arXiv:1009.0455v1 [gr-qc])'

On unitarity of a linearized Yang-Mills formulation for massless and massive gravity with propagating torsion. (arXiv:1009.0455v1 [gr-qc])

Fetched: September 2nd, 2010, 5:45am PDT by Rolando Gaitan Deveras

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A perturbative regime based on contortion as a dynamical variable and metric as a (classical) fixed background, is performed in the context of a pure Yang-Mills formulation for gravity in a $2+1$ dimensional space-time. In the massless case we show that the theory contains three degrees of freedom and only one is a non-unitary mode. Next, we introduce quadratical terms dependent on torsion, which preserve parity and general covariance. The linearized version reproduces an analogue Hilbert-Einstein-Fierz-Pauli unitary massive theory plus three massless modes, two of them represents non-unitary ones. Finally we confirm the existence of a family of unitary Yang-Mills-extended theories which are classically consistent with Einstein's solutions coming from non massive and topologically massive gravity. The unitarity of these YM-extended theories is shown in a perturbative regime. A possible way to perform a non-perturbative study is remarked.

Towards a Basis for Planar Two-Loop Integrals. (arXiv:1009.0472v1 [hep-th])

Fetched: September 2nd, 2010, 5:45am PDT by Janusz Gluza, Krzysztof Kajda, David A. Kosower

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The existence of a finite basis of algebraically independent one-loop integrals has underpinned important developments in the computation of one-loop amplitudes in field theories and gauge theories in particular. We give an explicit construction reducing integrals to a finite basis for planar integrals at two loops, both to all orders in the dimensional regulator e, and also when all integrals are truncated to O(e). We show how to reorganize integration-by-parts equations to obtain elements of the first basis efficiently, and how to use Gram determinants to obtain additional linear relations reducing this all-orders basis to the second one. The techniques we present should apply to non-planar integrals, to integrals with massive propagators, and beyond two loops as well.

Higher derivative corrections in holographic Zamolodchikov-Polchinski theorem. (arXiv:1009.0491v1 [hep-th])

Fetched: September 2nd, 2010, 5:45am PDT by Yu Nakayama

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We study higher derivative corrections in holographic dual of Zamolodchikov-Polchinski theorem that states the equivalence between scale invariance and conformal invariance in unitary d-dimensional Poincare invariant field theories. From the dual holographic perspective, we find that a sufficient condition to show the holographic theorem is the generalized strict null energy condition of the matter sector in effective (d+1)-dimensional gravitational theory. The same condition has appeared in the holographic dual of the ``c-theorem" and our theorem suggests a deep connection between the two, which was manifested in two-dimensional field theoretic proof of the both.

Equivariant Cohomology Of The Chiral de Rham Complex And The Half-Twisted Gauged Sigma Model. (arXiv:hep-th/0612164v3 UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Meng-Chwan Tan

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In this paper, we study the perturbative aspects of the half-twisted variant of Witten's topological A-model coupled to a non-dynamical gauge field with Kahler target space X being a G-manifold. Our main objective is to furnish a purely physical interpretation of the equivariant cohomology of the chiral de Rham complex, recently constructed by Lian and Linshaw in [arXiv:math/0501084], called the "chiral equivariant cohomology". In doing so, one finds that key mathematical results such as the vanishing in the chiral equivariant cohomology of positive weight classes, lend themselves to straightforward physical explanations. In addition, one can also construct topological invariants of X from the correlation functions of the relevant physical operators corresponding to the non-vanishing weight-zero classes. Via the topological invariance of these correlation functions, one can verify, from a purely physical perspective, the mathematical isomorphism between the weight-zero subspace of the chiral equivariant cohomology and the classical equivariant cohomology of X. Last but not least, one can also determine fully, the de Rham cohomology ring of X/G, from the topological chiral ring generated by the local ground operators of the physical model under study.

Five-Branes in M-Theory and a Two-Dimensional Geometric Langlands Duality. (arXiv:0807.1107v5 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Meng-Chwan Tan

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A recent attempt to extend the geometric Langlands duality to affine Kac-Moody groups, has led Braverman and Finkelberg [arXiv:0711.2083] to conjecture a mathematical relation between the intersection cohomology of the moduli space of G-bundles on certain singular complex surfaces, and the integrable representations of the Langlands dual of an associated affine G-algebra, where G is any simply-connected semisimple group. For the A-type groups, where the conjecture has been mathematically verified to a large extent, we show that the relation has a natural physical interpretation in terms of six-dimensional compactifications of M-theory with coincident five-branes wrapping certain hyperkahler four-manifolds; in particular, it can be understood as an expected invariance in the resulting spacetime BPS spectrum under string dualities. By replacing the singular complex surface with a smooth multi-Taub-NUT manifold, we find agreement with a closely related result demonstrated earlier via purely field-theoretic considerations by Witten. By adding OM five-planes to the original analysis, we argue that an analogous relation involving the non-simply-connected D-type groups, ought to hold as well. This is the first example of a string-theoretic interpretation of such a two-dimensional extension to complex surfaces of the geometric Langlands duality for the A-D groups.

Fierz-Pauli Mass From Torsion. (arXiv:0906.1733v3 [gr-qc] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Rolando Gaitan (UC)

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This paper has been withdrawn by the author due to imprecisions which must conduce to wrong results.

Gauge Theory of the full Lorentz Group on flat Spacetime. (arXiv:0906.2965v8 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Kay zum Felde

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We compute gauge theories of the Lorentz group. We discuss non-interacting, and interacting fermionic systems. The interacting system combines a local with a global Lorentz group, i.e, discusses a $SO(3,1)_{l}\times SO(3,1)_{g}$-theory. We compute the equations of motion and conservation laws for the fermionic matter current. The core of our work is the prediction of some new form of monopoles we call 'Dirac-Clifford-'t Hooft-Polyakov'-monopole. It resides in a state similar to color-flavor locking. Dirac-Clifford-'t Hooft-Polyakov-monopoles are invariant under global Lorentz transformations and are predicted to form vortices. The theory is renormalizable, since all Goldstone-Nambu modes are converted into massive vector gauge fields.

Covariant Vertex Operators for Cosmic Strings. (arXiv:0911.5354v2 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Dimitri Skliros, Mark Hindmarsh

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We construct complete sets of (open and closed string) covariant coherent state and mass eigenstate vertex operators in bosonic string theory. By minimally extending the standard definition of coherent states so as to include the string theory requirements, we show that the naive construction of the the closed string coherent states requires the existence of a lightlike compactification of spacetime. When the null winding states in the underlying Hilbert space are projected out the resulting vertex operators satisfy the definition of a coherent state and have a classical interpretation. We present explicitly both the covariant and lightcone gauge realization of the resulting states using the DDF map that relates the two. We also identify the corresponding general lightcone gauge classical solutions around which the quantum states are fluctuating. We go on to show that both the covariant gauge coherent vertex operators, the corresponding lightcone gauge coherent states and the classical solutions all share the same mass and angular momenta and conjecture that the covariant and lightcone gauge states are different manifestations of the same state and share identical interactions. This construction can be used to study the evolution of fundamental cosmic strings as predicted by string theory and may also be useful for other applications where massive string vertex operators are of interest.

Long life of Gauss-Bonnet corrected black holes. (arXiv:1004.3772v4 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by R. A. Konoplya, A. Zhidenko

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Dictated by the string theory and various higher dimensional scenarios, black holes in $D>4$-dimensional space-times must have higher curvature corrections. The first and dominant term is quadratic in curvature, and called the Gauss-Bonnet (GB) term. We shall show that although the Gauss-Bonnet correction changes black hole's geometry only softly, the emission of gravitons is suppressed by many orders even at quite small values of the GB coupling. The huge suppression of the graviton emission is due to the multiplication of the two effects: the quick cooling of the black hole when one turns on the GB coupling and the exponential decreasing of the grey-body factor of the tensor type of gravitons at small and moderate energies. At higher $D$ the tensor gravitons emission is dominant, so that the overall lifetime of black holes with Gauss-Bonnet corrections is many orders larger than it was expected. This effect might be observable at the future experiments in the Large Hadron Collider (LHC).

Flux tube delocalization at the deconfinement point. (arXiv:1004.3875v2 [hep-lat] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by M. Caselle

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We study the behaviour of the flux tube thickness in the vicinity of the deconfinement transition. We show, using effective string methods, that in this regime the square width increases linearly and not logarithmically with the interquark distance. The amplitude of this linear growth is an increasing function of the temperature and diverges as the deconfinement transition is approached from below. These predictions are in good agreement with a set of simulations performed in the 3d gauge Ising model.

Comments on the vacuum energy decay. (arXiv:1004.4867v3 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Enrique Álvarez, Roberto Vidal

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A very simple physical interpretation is given of the instability of vacuum energy as discussed recently by Polyakov. It is related to the existence of forbidden decays in de Sitter space, derived in some detail by Bros, Epstein and Moschella.

Gluon condensates and c, b quark masses from quarkonia ratios of moments. (arXiv:1004.5333v4 [hep-ph] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Stephan Narison (CNRS-IN2P3, Montpellier)

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We extract (for the first time) the ratio of the gluon condensate < g^3f_{abc}G^3 >/< alpha_s G^2 > expressed in terms of the liquid instanton radius rho_c from charmonium moments sum rules by examining the effects of < alpha_s G^2 > in the determinations of both rho_c and the running MS mass m_c(m_c). Using a global analysis of selected ratios of moments at different Q^2=0, 4m_c^2 and 8m_c^2 and taking < alpha_s G^2 > from 0.06 GeV^4, where the estimate of rho_c is almost independent of < alpha_s G^2 >, we deduce: rho_c=0.98(21) GeV^{-1} which corresponds to < g^3f_{abc}G^3 > = (31+- 13) GeV^2 < alpha_s G^2 >. The value of m_c(m_c) is less affected (within the errors) by the variation of < alpha_s G^2 >, where a common solution from different moments are reached for < alpha_s G^2 > greater than 0.02 GeV^4. Using the values of < alpha_s G^2 >=0.06(2) GeV^4 from some other channels and the previous value of < g^3f_{abc}G^3 >, we deduce: m_c(m_c)=1260(18) MeV and m_b(m_b)=4220(17) MeV, where an estimate of the 4-loops contribution has been included. Our analysis indicates that the errors in the determinations of the charm quark mass without taking into account the ones of the gluon condensates have been underestimated. To that accuracy, one can deduce the running light and heavy quark masses and their ratios evaluated at M_Z, where it is remarkable to notice the approximate equalities: m_s/m_u= m_b/m_s= m_t/m_b= 51(9), which might reveal some eventual underlying novel symmetry of the quark mass matrix in some Grand Unified Theories.

Three-loop HTL gluon thermodynamics at intermediate coupling. (arXiv:1005.1603v3 [hep-ph] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Jens O. Andersen, Nan Su, Michael Strickland

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We calculate the thermodynamic functions of pure-glue QCD to three-loop order using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature quantum field theory. We show that at three-loop order hard-thermal-loop perturbation theory is compatible with lattice results for the pressure, energy density, and entropy down to temperatures $T\simeq3\;T_c$. Our results suggest that HTLpt provides a systematic framework that can used to calculate static and dynamic quantities for temperatures relevant at LHC.

Summing Radiative Corrections to the Effective Potential. (arXiv:1005.1936v2 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by F.A. Chishtie, T. Hanif, Junji Jia, 1, D.G.C. McKeon, T.N. Sherry

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When one uses the Coleman-Weinberg renormalization condition, the effective potential $V$ in the massless $\phi_4^4$ theory with O(N) symmetry is completely determined by the renormalization group functions. It has been shown how the $(p+1)$ order renormalization group function determine the sum of all the N$^{\mbox{\scriptsize p}}$LL order contribution to $V$ to all orders in the loop expansion. We discuss here how, in addition to fixing the N$^{\mbox{\scriptsize p}}$LL contribution to $V$, the $(p+1)$ order renormalization group functions also can be used to determine portions of the N$^{\mbox{\scriptsize p+n}}$LL contributions to $V$. When these contributions are summed to all orders, the singularity structure of \mcv is altered. An alternate rearrangement of the contributions to $V$ in powers of $\ln \phi$, when the extremum condition $V^\prime (\phi = v) = 0$ is combined with the renormalization group equation, show that either $v = 0$ or $V$ is independent of $\phi$. This conclusion is supported by showing the LL, $\cdots$, N$^4$LL contributions to $V$ become progressively less dependent on $\phi$.

Lectures on Generalized Complex Geometry for Physicists. (arXiv:1006.1536v2 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Paul Koerber

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In these lectures we review Generalized Complex Geometry and discuss two main applications to string theory: the description of supersymmetric flux compactifications and the supersymmetric embedding of D-branes. We start by reviewing G-structures, and in particular SU(3)-structure and its torsion classes, before extending to Generalized Complex Geometry. We then discuss the supersymmetry conditions of type II supergravity in terms of differential conditions on pure spinors, and finally introduce generalized calibrations to describe D-branes. As examples we discuss in some detail AdS4 compactifications, which play a role as the geometric duals in the AdS4/CFT3-correspondence.

Gyratons on Melvin spacetime. (arXiv:1006.1794v3 [gr-qc] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Hedvika Kadlecova, Pavel Krtous

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We present and analyze new exact gyraton solutions of algebraic type II on a background which is static, cylindrically symmetric Melvin universe of type D. For a vanishing electromagnetic field it reduces to previously studied gyratons on Minkowski background. We demonstrate that the solutions are member of a more general family of the Kundt spacetimes. We show that the Einstein equations reduce to a set of mostly linear equations on a transverse 2-space and we discuss the properties of polynomial scalar curvature invariants which are generally non-constant but unaffected by the presence of gyratons.

The Leading Quantum Corrections to Stringy Kahler Potentials. (arXiv:1007.4793v3 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Lilia Anguelova, Callum Quigley, Savdeep Sethi

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The structure of stringy quantum corrections to four-dimensional effective theories is particularly interesting for string phenomenology and attempts to stabilize moduli. We consider the heterotic string compactified on a Calabi-Yau space. For this case, we compute the leading corrections to the kinetic terms of moduli fields. The structure of these corrections is largely dictated by the underlying higher-dimensional extended supersymmetry. We find corrections generically of order (alpha')^2 rather than of order (alpha')^3 found in type II compactifications or heterotic compactifications with the standard embedding. We explore the implications of these corrections for breaking no-scale structure.

Spectroscopy as a test of Coulomb's law - A probe of the hidden sector. (arXiv:1008.3536v2 [hep-ph] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Joerg Jaeckel, Sabyasachi Roy

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High precision spectroscopy can provide a sensitive tool to test Coulomb's law on atomic length scales. This can then be used to constrain particles such as extra "hidden" photons or minicharged particles that are predicted in many extensions of the standard model, and which cause small deviations from Coulomb's law. In this paper we use a variety of transitions in atomic hydrogen, hydrogenic ions, and exotic atoms to probe Coulomb's law. This extends the region of pure Coulomb's law tests to larger masses. For hidden photons and minicharged particles this region is already tested by other astrophysical and laboratory probes. However, future tests of true muonium and muonic atoms are likely to probe new parameter space and therefore have good discovery potential for new physics. Finally, we investigate whether the discrepancy between the theoretical calculation of the 2s_{1/2}^{F=1} - 2p_{3/2}^{F=2} transition in muonic hydrogen and its recent experimental measurement at PSI can be explained by the existence of a hidden photon. This explanation is ruled out by measurements of the Lamb shift in ordinary hydrogen.

The Photon Dispersion as an Indicator for New Physics ?. (arXiv:1008.3886v2 [hep-ph] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Wolfgang Bietenholz

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We first comment on the search for a deviation from the linear photon dispersion relation, in particular based on cosmic photons from Gamma Ray Bursts. Then we consider the non-commutative space as a theoretical concept that could lead to such a deviation, which would be a manifestation of Lorentz Invariance Violation. In particular we review a numerical study of pure U(1) gauge theory in a 4d non-commutative space. Starting from a finite lattice, we explore the phase diagram and the extrapolation to the continuum and infinite volume. These simultaneous limits - taken at fixed non-commutativity - lead to a phase of broken Poincare symmetry, where the photon appears to be IR stable, despite a negative IR divergence to one loop.

F(T) gravity and k-essence. (arXiv:1008.4486v2 [astro-ph.CO] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Ratbay Myrzakulov

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Modified teleparallel gravity theory with the torsion scalar have recently gained a lot of attention as a possible explanation of dark energy. We perform a thorough reconstruction analysis on the so-called $F(T)$ models, where $F(T)$ is some general function of the torsion term, and derive conditions for the equivalence between of $F(T)$ models with purely kinetic k-essence. We present a new class models of $F(T)$ - gravity and k-essence.

T-duality and dimensional reduction of S-brane solutions. (arXiv:1008.5220v3 [hep-th] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Riuji Mochizuki, Kenji Ikegami

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We studied dimensional reduction and T-duality in spacelike brane solutions of 10 or 11 dimensional supergravity, including spacelike counterparts of wave and monopole solutions. Dimensional reduction is well-defined if, and only if, the solutions possess static dimensions. However, T-duality is ill-defined for some of these solutions where dilaton expectation values depend on time. This led us to conclude that supergravity solutions should be regarded as low-energy solutions of superstring theory only if dilaton expectation values are independent of time.

Generalized Spin-Statistics Theorem. (arXiv:1008.5382v2 [cond-mat.stat-mech] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Lauri J. Suoranta

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We derive the spin-statistics theorem in both relativistic and non-relativistic first-quantized form for local field theories, extending considerably the earlier proofs. Our derivation is based on the representation theories of groups SU(2) and SL(2,C), latter being the universal covering of the Lorentz group. We include theories that have an internal symmetry group. We discuss relation to the standard representations of the Lorentz group and consistency of the non-relativistic limit. We formulate classical Majorana action in SL(2,C) and demonstrate that the failure to write it using the Dirac representation is simply a result of inexact notation. We discuss relation of the theorem to the canonical quantization. We also decouple the Dirac four-spinor representation to separate particle and anti-particle representations and discuss briefly a geometric proof of the CPT theorem.

Permalink for 'Determination of Dark Energy by the Einstein Telescope: Comparing with CMB, BAO and SNIa Observations. (arXiv:1009.0206v2 [astro-ph.CO] UPDATED)'

Determination of Dark Energy by the Einstein Telescope: Comparing with CMB, BAO and SNIa Observations. (arXiv:1009.0206v2 [astro-ph.CO] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by W. Zhao, C. Van Den Broeck, D. Baskaran, T.G.F. Li

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A design study is currently in progress for a third generation gravitational-wave (GW) detector called Einstein Telescope (ET). An important kind of source for ET will be the inspiral and merger of binary neutron stars (BNS) up to $z \sim 2$. If BNS mergers are the progenitors of short-hard $\gamma$-ray bursts, then some fraction of them will be seen both electromagnetically and through GW, so that the luminosity distance and the redshift of the source can be determined separately. An important property of these `standard sirens' is that they are \emph{self-calibrating}: the luminosity distance can be inferred directly from the GW signal, with no need for a cosmic distance ladder. Thus, standard sirens will provide a powerful independent check of the $\Lambda$CDM model. In previous work, estimates were made of how well ET would be able to measure a subset of the cosmological parameters (such as the dark energy parameter $w_0$) it will have access to, assuming that the others had been determined to great accuracy by alternative means. Here we perform a more careful analysis by explicitly using the potential Planck CMB data as prior information for these other parameters. We find that ET will be able to constrain $w_0$ and $w_a$ with accuracies $\Delta w_0 = 0.096$ and $\Delta w_a = 0.296$, respectively. These results are compared with projected accuracies for the JDEM Baryon Acoustic Oscillations (BAO) project and the SNAP Type Ia supernovae (SNIa) observations.

Matter and Dark Matter from False Vacuum Decay. (arXiv:1008.2355v1 [hep-ph] CROSS LISTED)

Fetched: September 2nd, 2010, 5:45am PDT by W. Buchmuller, K. Schmitz, G. Vertongen

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We study tachyonic preheating associated with the spontaneous breaking of B-L, the difference of baryon and lepton number. Reheating occurs through the decays of heavy Majorana neutrinos which are produced during preheating and in decays of the Higgs particles of B-L breaking. Baryogenesis is an interplay of nonthermal and thermal leptogenesis, accompanied by thermally produced gravitino dark matter. The proposed mechanism simultaneously explains the generation of matter and dark matter, thereby relating the absolute neutrino mass scale to the gravitino mass.

F(T) gravity and k-essence. (arXiv:1008.4486v2 [astro-ph.CO] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Ratbay Myrzakulov

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Thermal axion production in the primordial quark-gluon plasma. (arXiv:1008.4528v2 [hep-ph] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Peter Graf, Frank Daniel Steffen

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We calculate the rate for thermal production of axions via scattering of quarks and gluons in the primordial quark-gluon plasma. To obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling, we use systematic field theoretical methods such as hard thermal loop resummation and the Braaten-Yuan prescription. The thermally produced yield, the decoupling temperature, and the density parameter are computed for axions with a mass below 10 meV. In this regime, with a Peccei-Quinn scale above 6x10^8 GeV, the associated axion population can still be relativistic today and can coexist with the axion cold dark matter condensate.

Assembly History and Structure of Galactic Cold Dark Matter Halos. (arXiv:1008.5114v2 [astro-ph.CO] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Jie Wang, J. F. Navarro, C. S. Frenk, S. D. M. White, V. Springel, A. Jenkins, A. Helmi, A. Ludlow, M. Vogelsberger

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We use the Aquarius simulation series to study the imprint of assembly history on the structure of Galaxy-mass cold dark matter halos. Our results confirm earlier work regarding the influence of mergers on the mass density profile and the inside-out growth of halos. The inner regions that contain the visible galaxies are stable since early times and are significantly affected only by major mergers. Particles accreted diffusely or in minor mergers are found predominantly in the outskirts of halos. Our analysis reveals trends that run counter to current perceptions of hierarchical halo assembly. For example, major mergers (i.e. those with progenitor mass ratios greater than 1:10) contribute little to the total mass growth of a halo, on average less than 20 per cent for our six Aquarius halos. The bulk is contributed roughly equally by minor mergers and by "diffuse" material which is not resolved into individual objects. This is consistent with modeling based on excursion-set theory which suggests that about half of this diffuse material should not be part of a halo of any scale. Interestingly, the simulations themselves suggest that a significantly fraction is not truly diffuse, since it was ejected from earlier halos by mergers prior to their joining the main system. The Aquarius simulations resolve halos to much lower mass scales than are expected to retain gas or form stars. These results thus confirm that most of the baryons from which visible galaxies form are accreted diffusely, rather than through mergers, and they suggest that only relatively rare major mergers will affect galaxy structure at later times.

The impact of X-rays on molecular cloud fragmentation and the IMF. (arXiv:1008.5284v2 [astro-ph.GA] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by S. Hocuk, M. Spaans

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Star formation is regulated through a variety of feedback processes. In this study, we treat feedback by X-rays and discuss its implications. Our aim is to investigate whether star formation is significantly affected when a star forming cloud resides in the vicinity of a strong X-ray source. We perform an Eulerian grid simulation with embedded Lagrangian sink particles of a collapsing molecular cloud near a massive, 10^7 M_o black hole. The chemical and thermal changes caused by radiation are incorporated into the FLASH code. When there is strong X-ray feedback the star forming cloud fragments into larger clumps whereby fewer but more massive protostellar cores are formed. Competitive accretion has a strong impact on the mass function and a near-flat, non-Salpeter IMF results.

Near-infrared Thermal Emission from WASP-12b: detections of the secondary eclipse in Ks, H & J. (arXiv:1009.0071v2 [astro-ph.EP] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Bryce Croll (University of Toronto), David Lafreniere (UdeM), Loic Albert (CFHT), Ray Jayawardhana (UofT), Jonathan J. Fortney (UCSC), Norman Murray (CITA)

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We present Ks, H & J-band photometry of the very highly irradiated hot Jupiter WASP-12b using the Wide-field Infrared Camera on the Canada-France-Hawaii telescope. Our photometry brackets the secondary eclipse of WASP-12b in the Ks and H-bands, and in J-band starts in mid-eclipse and continues until well after the end of the eclipse. We detect its thermal emission in all three near-infrared bands. Our secondary eclipse depths are 0.309 +/- 0.013% in Ks-band (24-sigma), 0.176 +/- 0.020% in H-band (9-sigma) and 0.131 +/- 0.028% in J-band (4-sigma). All three secondary eclipses are best-fit with a consistent phase that is compatible with a circular orbit. By combining our secondary eclipse times with others published in the literature, as well as the radial velocity and transit timing data for this system, we show that there is no evidence that WASP-12b is precessing at a detectable rate, and show that its orbital eccentricity is likely zero. Our thermal emission measurements also allow us to constrain the characteristics of the planet's atmosphere; our Ks-band eclipse depth argues in favour of inefficient day to nightside redistribution of heat and a low Bond albedo for this very highly irradiated hot Jupiter. The J and H-band brightness temperatures are slightly cooler than the Ks-band brightness temperature, and thus hint at the possibility of a modest temperature inversion deep in the atmosphere of WASP-12b; the high pressure, deep atmospheric layers probed by our J and H-band observations are likely more homogenized than the higher altitude layer. Lastly, our best-fit Ks-band eclipse has a marginally longer duration than would otherwise be expected; this may be tentative evidence for material being tidally stripped from the planet - as was predicted for this system by Li & collaborators, and for which observational confirmation was recently arguably provided by Fossati & collaborators.

Permalink for 'VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies III: the atlas of the stellar and ionized gas distribution. (arXiv:1009.0112v2 [astro-ph.CO] UPDATED)'

VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies III: the atlas of the stellar and ionized gas distribution. (arXiv:1009.0112v2 [astro-ph.CO] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by Javier Rodriguez Zaurin, Santiago Arribas, Ana Monreal Ibero, Luis Colina, Almudena Alonso Herrero, Julia Alfonso Garzon

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LIRGs and ULIRGs are much more numerous at higher redshifts than locally, dominating the star-formation rate density at redshifts ~1 - 2. Therefore, they are important objects in order to understand how galaxies form and evolve through cosmic time. We aim to characterize the morphologies of the stellar continuum and the ionized gas (H_alpha) emissions from local sources, and investigate how they relate with the dynamical status and IR-luminosity of the sources. We use optical (5250 -- 7450 \AA) integral field spectroscopic (IFS) data for a sample of 38 sources, taken with the VIMOS instrument, on the VLT. We present an atlas of IFS images of continuum emission, H_alpha emission, and H_alpha equivalent widths for the sample. The H_alpha images frequently reveal extended structures that are not visible in the continuum, such as HII regions in spiral arms, tidal tails, rings, of up to few kpc from the nuclear regions. The morphologies of the continuum and H_alpha images are studied on the basis of the C_{2kpc} parameter, which measures the concentration of the emission within the central 2 kpc. The C_{2kpc} values found for the H_alpha images are higher than those of the continuum for the majority (85%) of the objects in our sample. On the other hand, most of the objects in our sample (~62%) have more than half of their H_alpha emission outside the central 2 kpc. No clear trends are found between the values of C_{2kpc} and the IR-luminosity of the sources. On the other hand, our results suggest that the star formation in advance mergers and early-stage interactions is more concentrated than in isolated objects. We compared the H_alpha and infrared emissions as tracers of the star-formation activity. We find that the star-formation rates derived using the H_alpha luminosities generally underpredict those derived using the IR luminosities, even after accounting for reddening effects.

Determination of Dark Energy by the Einstein Telescope: Comparing with CMB, BAO and SNIa Observations. (arXiv:1009.0206v2 [astro-ph.CO] UPDATED)

Fetched: September 2nd, 2010, 5:45am PDT by W. Zhao, C. Van Den Broeck, D. Baskaran, T.G.F. Li

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Fetched: September 2nd, 2010, 5:45am PDT by Francesco Sannino (CP3-Origins), Joseph Schechter (Syracuse University)

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Fetched: September 2nd, 2010, 5:45am PDT by Anzhong Wang, Qiang Wu

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Fetched: September 2nd, 2010, 5:45am PDT by Kazuo Hosomichi, Sungjay Lee, Jaemo Park

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Fetched: September 2nd, 2010, 5:45am PDT by Spyros Basilakos, Saurya Das, Elias C. Vagenas

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