We have measured thermoelectric power (TEP) as a function of hole concentration per CuO2 layer, Ppl, in Y1-xCaxBa2Cu3O6 (Ppl = x/2) with no oxygen in the Cu-O chain layer. The room-temperature TEP as a function of Ppl, S290(Ppl), of Y1-xCaxBa2Cu3O6 behaves identically to that of La2-zSrzCuO4 (Ppl = z). We argue that S290(Ppl) represents a measure of the intrinsic equilibrium electronic states of doped holes and, therefore, can be used as a common scale for the carrier concentrations of layered cuprates. We shows that the Ppl determined by this new universal scale is consistent with both hole concentration microscopically determined by NQR and the hole concentration macroscopically determined by the Cu valency. We find two characteristic scaling temperatures, TS* and TS2*, in the TEP vs. temperature curves that change systematically with doping. Based on the universal scale, we uncover a universal phase diagram in which almost all the experimentally determined pseudogap temperatures as a function of Ppl fall on two common curves; upper pseudogap temperature defined by the TS* versus Ppl curve and lower pseudogap temperature defined by the TS2* versus Ppl curve. We find that while pseudogaps are intrinsic properties of doped holes of a single CuO2 layer for all high-Tc cuprates, Tc depends on the number of layers, therefore the inter-layer coupling, in each individual system.
We consider EGO as a possible third-generation ground-based gravitational wave detector and evaluate its capabilities for the detection and interpretation of compact binary inspiral signals. We identify areas of astrophysics and cosmology where EGO would have qualitative advantages, using Advanced LIGO as a benchmark for comparison.
The radial component of the motion of compact binary systems composed of neutron stars and/or black holes on eccentric orbit is integrated. We consider all type of perturbations that emerge up to second post-Newtonian order. These perturbations are either of relativistic origin or are related to the spin, mass quadrupole and magnetic dipole moments of the binary components. We derive a generalized Kepler equation and investigate its domain of validity, in which it properly describes the radial motion.
Supersymmetric extensions of the Standard Model predict the existence of Q-balls with baryon and lepton numbers. Stable Q-balls can form at the end of inflation from the fragmentation of the Affleck-Dine condensate and can exist as dark matter. The best current limits come from Super-Kamiokande and MACRO. The search beyond these limits can be conducted using the future water Cherenkov detectors.
We determine the abundance of the lightest (dark matter) sterile neutrinos created in the Early Universe due to active-sterile neutrino transitions from the thermal plasma. Our starting point is the field-theoretic formula for the sterile neutrino production rate, derived in our previous work [JHEP 06(2006)053], which allows to systematically incorporate all relevant effects, and also to analyse various hadronic uncertainties. Our numerical results differ moderately from previous computations in the literature, and lead to an absolute upper bound on the mixing angles of the dark matter sterile neutrino. Comparing this bound with existing astrophysical X-ray constraints, we find that the Dodelson-Widrow scenario, which proposes sterile neutrinos generated by active-sterile neutrino transitions to be the sole source of dark matter, is only possible for sterile neutrino masses lighter than 3.5 keV (6 keV if all hadronic uncertainties are pushed in one direction and the most stringent X-ray bounds are relaxed by a factor of two). This upper bound may conflict with a lower bound from structure formation, but a definitive conclusion necessitates numerical simulations with the non-equilibrium momentum distribution function that we derive. If other production mechanisms are also operative, no upper bound on the sterile neutrino mass can be established.
Mach's principle is the concept that inertial frames are determined by matter. We propose and implement a precise formulation of Mach's principle in which matter and geometry are in one-to-one correspondence. Einstein's equations are not modified and no selection principle is applied to their solutions; Mach's principle is realized wholly within Einstein's general theory of relativity. The key insight is the observation that, in addition to bulk matter, one can also add boundary matter. Specification of both boundary and bulk stress tensors uniquely specifies the geometry and thereby the inertial frames. Our framework is similar to that of the black hole membrane paradigm and, in asymptotically AdS space-times, is consistent with holographic duality.
Unless our universe is decaying at an astronomical rate (i.e., on the present cosmological timescale of Gigayears, rather than on the quantum recurrence timescale of googolplexes), it would apparently produce an infinite number of observers per comoving volume by thermal or vacuum fluctuations (Boltzmann brains). If the number of ordinary observers per comoving volume is finite, this scenario seems to imply zero likelihood for us to be ordinary observers and minuscule likelihoods for our actual observations. Hence, our observations suggest that this scenario is incorrect and that perhaps our universe is decaying at an astronomical rate.
We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter which are based on improved approximations schemes. The potential matrix elements have been adapted for isospin asymmetric nuclear matter in order to account for the proton-neutron mass splitting in a more consistent way. The proton properties are particularly sensitive to this adaption and its consequences, whereas the neutron properties remains almost unaffected in neutron rich matter. Although at present full Brueckner calculations are still too complex to apply to finite nuclei, these relativistic Brueckner results can be used as a guidance to construct a density dependent relativistic mean field theory, which can be applied to finite nuclei. It is found that an accurate reproduction of the Dirac-Brueckner-Hartree-Fock equation of state requires a renormalization of these coupling functions.
Based on the standard transfer matrix, a formally exact quantization condition for arbitrary potentials, which outflanks and unifies the historical approaches, is derived. It can be used to find the exact bound-state energy eigenvalues of the quantum system without solving an equation of motion for the system wave functions.
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We study the conditions required for validity of the generalized second law in phantom dominated universe in the presence of Schwarzschild black hole. Our study is independent of the origin of the phantom like behavior of the considered universe. We also discuss the generalized second law in the neighborhood of transition (from quintessence to phantom regime) time. We show that even for a constant equation of state parameter the generalized second law may be satisfied provided the temperature is not taken as de Sitter temperature. It is shown that in models with (only) a transition from quintessence to phantom regime the generalized second law does not hold in the transition epoch.
The Parametrized Post-Newtonian expansion of gravitational theories with a scalar field coupled to the Gauss-Bonnet invariant is performed and confrontation of such theories with Solar system experiments is discussed.
In this paper we obtain the black hole metric from a semiclassical analysis of loop quantum black hole. Our solution and the Schwarzschild one tend to match well at large distances from Planck region. In r=0 the semiclassical metric is regular and singularity free in contrast to the classical one. By using the new metric we calculate the Hawking temperature and the entropy. For the entropy we obtain the logarithmic correction to the classical area law. Finally we study the mass evaporation process and we show the mass and temperature tend to zero at infinitive time.
We study the formation of black strings from a gravitational collapse of cylindrical dust clouds in the three-dimensional low-energy string theory. A new junction condition for the dilaton as well as two junction conditions for metrics and extrinsic curvatures between both regions of the clouds is presented. As a consequence, it is found that the collapsing dust cloud always collapses to a black string within a finite collapse time, and then a curvature singularity formed at origin is cloaked by an event horizon. Moreover, it is also found that the collapse process can form a naked singularity within finite time, regardless of the choice of initial data.
Field theories which violate the null energy condition (NEC) are of interest for the solution of the cosmological singularity problem and for models of cosmological dark energy with the equation of state parameter $w<-1$. We discuss the consistency of two recently proposed models that violate the NEC. The ghost condensate model requires higher-order derivative terms in the action. It leads to a heavy ghost field and unbounded energy. We estimate the rates of particles decay and discuss possible mass limitations to protect stability of matter in the ghost condensate model. The nonlocal stringy model that arises from a cubic string field theory and exhibits a phantom behavior also leads to unbounded energy. In this case the spectrum of energy is continuous and there are no particle like excitations. This model admits a natural UV completion since it comes from superstring theory.
This is the second paper in the series that confronts predictions of a model of the landscape with cosmological observations. We show here how the modifications of the Friedmann equation due to the decohering effects of long wavelength modes on the wavefunction of the Universe defined on the landscape leave unique signatures on the CMB spectra and large scale structure (LSS). We show that the effect of the string corrections is to suppress $\sigma_8$ and the CMB $TT$ spectrum at large angles, thereby bringing WMAP and SDSS data for $\sigma_8$ into agreement. We find interesting features imprinted on the matter power spectrum $P(k)$: power is suppressed at large scales indicating the possibility of primordial voids competing with the ISW effect. Furthermore, power is enhanced at structure and substructure scales, $k\simeq 10^{-2-0} h~{\rm Mpc}^{-1}$. Our smoking gun for discriminating this proposal from others with similar CMB and LSS predictions come from correlations between cosmic shear and temperature anisotropies, which here indicate a noninflationary channel of contribution to LSS, with unique ringing features of nonlocal entanglement displayed at structure and substructure scales.
During the collapse of massive stars, and the supernova type-II explosions, stellar matter reaches densities and temperatures which are similar to the ones obtained in intermediate-energy nucleus-nucleus collisions. The nuclear multifragmentation reactions can be used for determination of properties of nuclear matter at subnuclear densities, in the region of the nuclear liquid-gas phase transition. It is demonstrated that the modified properties of hot nuclei (in particular, their symmetry energy) extracted from the multifragmentation data can essentially influence nuclear composition of stellar matter. The effects on weak processes, and on the nucleosynthesis are also discussed.
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We consider the minimal supersymmetric standard model (MSSM) extended by introducing three right-handed (s)neutrinos to account for neutrino masses in the oscillation experiments. Assuming that the neutrino masses are purely Dirac-type, the lightest right-handed sneutrino $\tilde \nu_R$ can be the lightest superparticle (LSP), which is a good candidate of cold dark matter (CDM) of the universe. We study the possibility of realizing $\tilde \nu_R$-CDM, paying a special attention to the production of $\tilde \nu_R$ via decay of the next-to-lightest superparticle (NLSP) after its freeze-out time. It is shown that the late decay of the MSSM-LSP (the LSP among superparticles in the MSSM) can produce a sufficient amount of $\tilde \nu_R$ to explain the observed dark-matter density, and that the $\tilde \nu_R$-CDM scenario can be realized in a wide range of parameter space. We also consider the constraint on the decay of MSSM-LSP from the big-bang nucleosynthesis (BBN); we found that the case with stau being the MSSM-LSP is severely constrained.
In this paper we extend our previous treatment of the one-loop corrections to inflation. Previously we calculated the one-loop corrections to the background and the two-point correlation function of inflaton fluctuations in a specific model of chaotic inflation. We showed that the loop corrections depend on the total number of e-foldings and estimated that the effect could be as large as a few percent in a lambda-phi-four model of chaotic inflation. In the present paper we generalize the calculations to general inflationary potentials. We find that effect can be as large as 35% in the simplest model of chaotic inflation with a quadratic inflationary potential. We discuss the physical interpretation of the effect in terms of the tensor-to-scalar consistency relation. Finally, we discuss the relation to the work of Weinberg on quantum contributions to cosmological correlators.
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The generation of gravitational waves during inflation due to the non-linear coupling of scalar and tensor modes is discussed. Two formalisms are used and compared: a covariant and local approach, as well as a metric-based analysis. An application to slow-roll inflation is also described.
We show that reheating of the universe occurs spontaneously in a broad class of inflation models with f(phi)R gravity (phi is inflaton). The model does not require explicit couplings between phi and bosonic or fermionic matter fields. The couplings arise spontaneously when phi settles in the vacuum expectation value (vev) and oscillates, with coupling constants given by derivatives of f(phi) at the vev and the mass of resulting bosonic or fermionic fields. This mechanism allows inflaton quanta to decay into any fields which are not conformally invariant in f(phi)R gravity theories.
We analyze the left-right symmetric type I+II seesaw mechanism, where an eight-fold degeneracy among the mass matrices of heavy right handed neutrinos M_R is known to exist. Using the stability property of the solutions and their ability to lead to successful baryogenesis via leptogenesis as additional criteria, we discriminate among these eight solutions and partially lift their eight-fold degeneracy. In particular, we find that viable leptogenesis is generically possible for four out of the eight solutions.
We study 2-field inflation models based on the ``large-volume'' flux compactification of type IIB string theory. The role of the inflaton is played by a K\"ahler modulus \tau corresponding to a 4-cycle volume and its axionic partner \theta. The freedom associated with the choice of Calabi Yau manifold and the non-perturbative effects defining the potential V(\tau, \theta) and kinetic parameters of the moduli bring an unavoidable statistical element to theory prior probabilities within the low energy landscape. The further randomness of (\tau, \theta) initial conditions allows for a large ensemble of trajectories. Features in the ensemble of histories include ``roulette tractories'', with long-lasting inflations in the direction of the rolling axion, enhanced in number of e-foldings over those restricted to lie in the \tau-trough. Asymptotic flatness of the potential makes possible an eternal stochastic self-reproducing inflation. A wide variety of potentials and inflaton trajectories agree with the cosmic microwave background and large scale structure data. In particular, the observed scalar tilt with weak or no running can be achieved in spite of a nearly critical de Sitter deceleration parameter and consequently a low gravity wave power relative to the scalar curvature power.
We consider models where moduli fields are not stabilized and play the role of quintessence. In order to evade gravitational tests, we investigate the possibility that moduli behave as chameleon fields. We find that, for realistic moduli superpotentials, the chameleon effect is not strong enough, implying that moduli quintessence models are gravitationally ruled out. More generally, we state a no-go theorem for quintessence in supergravity whereby models either behave like a pure cosmological constant or violate gravitational tests
I detected a very strong (25 %var) period of 3592+-57 years at 99% confidence level in the 10Be deposition rates from Vostok, Antarctica ice core raw (gapped, unaltered) data. The period was verified at 99% confidence level against the 10Be concentration raw data at both Vostok, as 3700+-57 years at very strong 38 %var, and Taylor Dome, Antarctica, as 3800+-61 years at very strong 23 %var. The noisy Mg concentration data from Taylor Dome also show an extremely strong (44 %var) period of 3965+-16 years. The Vostok data also show the Hallstadzeit Solar cycle, as 2296+-57 years at 12 %var, perhaps its best estimate yet. I use for all analyses the 99% confidence strict Gauss-Vanicek spectral analysis (GVSA) that estimates periods in incomplete records. Based on recent 500-parsec Galactic Center (GC) GeV/TeV Gamma ray surveys by the H.E.S.S. and INTEGRAL telescopes, the GC extremely active central region makes the best candidate host for bursts leaving the discovered signature. A previously reported 3600 years period in geomagnetic field declinations could support this conclusion by indicating that the discovered phase could perhaps overpower entire astronomical magnetic fields, even at distances close to GC-Earth. I also estimate using GVSA-specific features the epoch of the most recent 10Be maximum on Earth as 1085+-57 CE, coinciding with the 1054-1056 CE historical account by Asian astronomers of a sky explosion believed/disputed to mean the Crab supernova SN1054 event. I predict the next maximum raw 10Be on Earth in year 4463+-57 CE, indicating that the current climate change is not cosmogenic, thus allowing for the conventional (anthropogenic) view. I conclude that, if real, it may be possible for such recurring Galactic bursts to affect the Earth climate significantly.
Great opportunities arise for teaching physics, astronomy, and their histories when new discoveries are made that involve concepts accessible to students at every level. Such an opportunity currently exists thanks to the fact that notes written by Galileo indicating that he observed the double star Mizar in the "Big Dipper" have recently come to light. His measurements of this star, given the scientific knowledge at the time, strongly supported the theory that the Earth was fixed in space and not moving. Had Galileo published these results, it is likely that widespread acceptance of the heliocentric theory in scientific circles would have been significantly delayed. In light of these notes, his later reference in his Dialogue to using double stars as a means of proving that the Earth was in motion is puzzling. The physics and mathematics behind Galileo's work is easily within reach of students in introductory physics and astronomy courses, so discussion of Galileo's Mizar work and its interesting implications can be used in virtually any class.
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We present an approach to the problem of vacuum energy in cosmology, based on dynamical screening of Lambda on the horizon scale. We review first the physical basis of vacuum energy as a phenomenon connected with macroscopic boundary conditions, and the origin of the idea of its screening by particle creation and vacuum polarization effects. We discuss next the relevance of the quantum trace anomaly to this issue. The trace anomaly implies additional terms in the low energy effective theory of gravity, which amounts to a non-trivial modification of the classical Einstein theory, fully consistent with the Equivalence Principle. We show that the new dynamical degrees of freedom the anomaly contains provide a natural mechanism for relaxing Lambda to zero on cosmological scales. We consider possible signatures of the restoration of conformal invariance predicted by the fluctuations of these new scalar degrees of freedom on the spectrum and statistics of the CMB, in light of the latest bounds from WMAP. Finally we assess the prospects for a new cosmological model in which the dark energy adjusts itself dynamically to the cosmological horizon boundary, and therefore remains naturally of order H^2 at all times without fine tuning.
The generalized second law of gravitational thermodynamics is examined in scenarios where the dark energy dominates the cosmic expansion. For quintessence and phantom fields this law is fulfilled but it may fail when the dark energy is in the form of a Chaplygin gas. However, if a black hole is allowed in the picture, the law can be violated if the field is of phantom type.
General relativity and quantum mechanics provide a natural explanation for the existence of dark energy with its observed value and predict its dynamics. Dark energy proves to be necessary for the existence of space-time itself and determines the rate of its stability.
To investigate the imprint on the gravitational-wave emission from extreme mass-ratio inspirals in non-pure Kerr spacetimes, we have studied the ``kludge'' waveforms generated in highly-accurate and numerically-generated spacetimes containing a black hole and a self-gravitating torus with comparable mass and spin. In order to maximize their impact on the produced waveforms, we have considered tori that are compact, massive and close to the central black hole, investigating under what conditions the LISA experiment could detect their presence. Our results show that for a large portion of the space of parameters the waveforms produced by EMRIs in these black hole-torus systems are indistinguishable from pure-Kerr waveforms. Hence, a ``confusion problem'' will be present for observations carried out over a timescale below or comparable to the dephasing time.
We show that the causal set approach to creating an ever-present cosmological 'constant' in the expanding universe is strongly constrained by the isotropy of the microwave background. Fluctuations generated by stochastic lambda generation which are consistent with COBE and WMAP observations are far too small to dominate the expansion dynamics at z<1000 and so cannot explain the observed late-time acceleration of the universe. We also discuss other observational constraints from the power spectrum of galaxy clustering and show that the theoretical possibility of ever-present lambda arises only in 3+1 dimensional space-times.
We present a scenario in which a remarkably simple relation linking dark matter properties and neutrino masses naturally emerges. This framework points towards a low energy theory where the neutrino mass originates from the existence of a light scalar dark matter particle in the MeV mass range. A very surprising aspect of this scenario is that the required MeV dark matter is one of the favoured candidates to explain the mysterious emission of 511 keV photons in the centre of our galaxy. A possible interpretation of these findings is that dark matter is the stepping stone of a theory beyond the standard model instead of being an embarrassing relic whose energy density must be accounted for in any successful model building.
We study the decay of the inflaton in no-scale supergravity and show that decay due to the gravitational interactions through supergravity effects is highly suppressed relative to the case in minimal supergravity or models with a generic Kahler potential. We also show that decay to gravitinos is suppressed. We demonstrate that decay and sufficient reheating are possible with the introduction of a non-trivial gauge kinetic term. This channel may be dominant in no-scale supergravity, yet yields a re-heating temperature which is low enough to avoid the gravitino problem while high enough for Big Bang Nucleosynthesis and baryogenesis.
We discuss a model which gives rise to cosmic self-acceleration due to modified gravity. Improvements introduced by this approach are the following: In the coordinate system commonly used, the metric does not grow in the bulk, and no negative mass states are expected to appear. The spectrum of small perturbations contains a localized massless tensor mode, but does not admit dangerous localized massive gravitons. All the massive spin-2 modes are continuum states. The action of the model, which is an extension of DGP, allows to relax the previously known constraint on the bulk fundamental scale of gravity. The latter can take any value below the 4D Planck mass.
We study the landscape models of eternal inflation with an arbitrary number of different vacua states, both recyclable and terminal. We calculate the abundances of bubbles following different geodesics. We show that the results obtained from generic time-like geodesics have undesirable dependence on initial conditions. In contrast, the predictions extracted from ``eternal'' geodesics, which never enter terminal vacua, do not suffer from this problem. We derive measure equations for ensembles of geodesics and discuss possible interpretations of initial conditions in eternal inflation.
In this thesis, I study the phase diagram of dense, locally neutral three-flavor quark matter as a function of the strange quark mass, the quark chemical potential, and the temperature, employing a general nine-parameter ansatz for the gap matrix. I also study the phase diagram of dense, locally neutral three-flavor quark matter within the framework of a Nambu-Jona-Lasinio (NJL) model. In the analysis, dynamically generated quark masses are taken into account self-consistently. The phase diagram in the plane of temperature and quark chemical potential is presented. In addition, I study the effect of neutrino trapping on the phase diagram of dense, locally neutral three-flavor quark matter within the same NJL model. The phase diagrams in the plane of temperature and quark chemical potential, as well as in the plane of temperature and lepton-number chemical potential are presented. The implications of these results for the evolution of protoneutron stars are briefly discussed.
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