118103986
Aspects of the string theory landscape: Compactification and evolution
1748432
Dynamical dimension change in supercritical string theory
We study tree-level solutions to heterotic string theory in which the number of spacetime dimensions 10+n changes dynamically due to closed string tachyon condensation. Taking the large-n limit, we compute the amount by which the dilaton gradient changes during the condensation process. At leading order in n we find that the change in the invariant magnitude of the dilaton gradient compensates the change in spacelike central charge on the worldsheet, so that the total worldsheet central charges are equal at early and late times. This result supports our interpretation of the worldsheet theory as a CFT of critical central charge which describes a dynamical reduction in the total number of spacetime dimensions.
18223996
Beauty is attractive: Moduli trapping at enhanced symmetry points
We study quantum effects on moduli dynamics arising from the production of particles which are light at points of enhanced symmetry in moduli space. The resulting forces trap the moduli at these points. Moduli trapping occurs in time-dependent quantum field theory, as well as in systems of moving D-branes, where it leads the branes to combine into stacks. Trapping also occurs in the presence of gravity, though the range over which the moduli can roll is limited by Hubble friction. We observe that a scalar field trapped on a steep potential can induce a stage of acceleration of the universe, which we call trapped inflation. Moduli trapping ameliorates the cosmological moduli problem and may affect vacuum selection. In particular, rolling moduli are most powerfully attracted to the points of greatest symmetry. Given suitable assumptions about the dynamics of the very early universe, this effect might help to explain why among the plethora of possible vacuum states of string theory, we appear to live in one with a large number of (spontaneously broken) symmetries.
118774140
On the Vacuum Propagation of Gravitational Waves
We show that, for any local, causal quantum field theory which couples covariantly to gravity, and which admits Minkowski spacetime vacuum(a) invariant under the inhomogeneous proper orthochronous Lorentz group, plane gravitational waves propagating in such Minkowski vacuum(a) do not dissipate energy or momentum via quantum field theoretic effects.
14174042
Gravity duals of Lifshitz-like fixed points
We find candidate macroscopic gravity duals for scale-invariant but non-Lorentz invariant fixed points, which do not have particle number as a conserved quantity. We compute two-point correlation functions which exhibit novel behavior relative to their AdS counterparts, and find holographic renormalization group flows to conformal field theories. Our theories are characterized by a dynamical critical exponent z, which governs the anisotropy between spatial and temporal scaling t {yields} {lambda}{sup z}t, x {yields} {lambda}x; we focus on the case with z = 2. Such theories describe multicritical points in certain magnetic materials and liquid crystals, and have been shown to arise at quantum critical points in toy models of the cuprate superconductors. This work can be considered a small step towards making useful dual descriptions of such critical points.
116542103
First estimate of producing the charmed baryon $\Lambda_c(2880)$ at PANDA
In the present work we explore the production potential of $\Lambda_c(2880)^+$ at PANDA. With the $J^P=\frac{5}{2}^+$ assignment to $\Lambda_c(2880)^+$, we calculate the differential and total cross sections of $p\bar{p}\to \Lambda_c^-\Lambda_c(2880)^+$. We also perform the Dalitz plot analysis and give the $pD^0$ invariant mass spectrum distribution of the process $p\bar{p}\to \Lambda_c^-pD^0$, where the signal and background contributions are considered. Our numerical results indicate that the production of $\Lambda_c(2880)^+$ may reach up to about 20 $\mu$b. About $10^7$ events from the reconstruction of $pD^0$ can be accumulated per day, if taking the designed luminosity ($2\times10^{32}~\mbox{cm}^{-2}\mbox{s}^{-1}$) of PANDA.
118578199
$Z_b(10610)$ and $Z_b(10650)$ structures produced by the initial single pion emission in the $\Upsilon(5S)$ decays
We propose an unique mechanism called {\it Initial Single Pion Emission} existing in the $\Upsilon(5S)$ decays, and further study the line shapes of $d\Gamma(\Upsilon(5S\to \Upsilon(nS)\pi^+\pi^-))/dm_{\Upsilon(nS)\pi^+}$ ($n=1,2,3$) and $d\Gamma(\Upsilon(5S\to h_b(mP)\pi^+\pi^-))/dm_{h_b(mP)\pi^+}$ ($m=1,2$). We find sharp structures around 10610 MeV and 10650 MeV in the obtained theoretical line shapes of $d\Gamma(\Upsilon(5S\to \Upsilon(nS)\pi^+\pi^-))/dm_{\Upsilon(nS)\pi^+}$ and $d\Gamma(\Upsilon(5S\to h_b(mP)\pi^+\pi^-))/dm_{h_b(mP)\pi^+}$ distributions, which could naturally correspond to the $Z_b(10610)$ and $Z_b(10650)$ structures newly observed by Belle.
117904233
The second Chern class in Spinning System
Topological property in a spinning system should be directly associated with its wavefunction. A complete decomposition formula of SU(2) gauge potential in terms of spinning wavefunction is established rigorously. Based on the $\phi $-mapping theory and this formula, one proves that the second Chern class is inherent in the spinning system. It is showed that this topological invariant is only determined by the Hopf index and Brouwer degree of the spinning wavefunction.
14284439
X(1812)in the quarkonia-glueball-hybrid mixing scheme
Recently a $J^{PC}=0^{++}$ (X(1812)) state with a mass near the threshold of $\omega$ and $\phi$ has been observed by the BES collaboration in $J/\psi \to \gamma \omega \phi$ decay. It has been suggested that it is a $I^G = 0^+$ state. If it is true, this state fits in a mixing scheme based on quarkonia, glueball and hybrid (QGH) very nicely where five physical states are predicted. Together with the known $f_0(1370)$, $f_0(1500)$, $f_0(1710)$, and $f_0(1790)$ states, X(1812) completes the five members in this family. Using known experimental data on these particles we determine the ranges of the mixing parameters and predict decay properties for X(1812). We also discuss some features which may be able to distinguish between four-quark and hybrid mixing schemes.
118492896
The dark secrets of gaseous nebulae -- highlights from deep spectroscopy
In this contribution, I will briefly review the development of the theory of photoionized gaseous nebulae, highlighting some of the key events. I will then present some recent developments of deep spectroscopy of planetary nebulae (PNe) and H II regions, concentrating on observations of faint heavy element optical recombination lines (ORLs). I will show that there is strong evidence that nebulae contain another previously unknown component of cold (about 1,000 K), high-metallicity plasma, probably in the form of H-deficient inclusions embedded in the warm (about 10,000 K) diffuse nebula of "normal (i.e. near solar) composition". This cold gas emits essentially all the observed fluxes of heavy element ORLs, but is too cool to excite any significant optical or ultraviolet collisionally excited lines (CELs) and thus invisible via the latter. The existence of H-deficient gas in PNe and probably also in H II regions, not predicted by the current stellar evolution theory, provides a natural solution to the long-standing dichotomy between nebular plasma diagnostics and abundance determinations using CELs on the one hand and ORLs on the other, a discrepancy that is ubiquitously observed in Galactic and extragalactic PNe as well as H II regions.