X-ray Raman compression via two-stream instability in dense plasmas

A Raman compression scheme suitable for x-rays, where the Langmuir wave is created by an intense beam rather than the pondermotive potential between the seed and pump pulses, is proposed. The required intensity of the seed and pump pulses enabling the compression could be mitigated by more than a factor of 100, compared to conventionally available other Raman compression schemes. The relevant wavelength of x-rays ranges from 1 to 10 nm

Red blood cells and other non-spherical capsules in shear flow: oscillatory dynamics and the tank-treading-to-tumbling transition

We consider the motion of red blood cells and other non-spherical microcapsules dilutely suspended in a simple shear flow. Our analysis indicates that depending on the viscosity, membrane elasticity, geometry and shear rate, the particle exhibits either tumbling, tank-treading of the membrane about the viscous interior with periodic oscillations of the orientation angle, or intermittent behavior in which the two modes occur alternately. For red blood cells, we compute the complete phase diagram and identify a novel tank-treading-to-tumbling transition at low shear rates. Observations of such motions coupled with our theoretical framework may provide a sensitive means of assessing capsule properties.Comment: 11 pages, 4 figure

Traversable wormhole in the deformed Ho\v{r}ava-Lifshitz gravity

Asymptotically flat wormhole solutions are found in the deformed Ho\v{r}ava-Lifshitz gravity. It turns out that higher curvature terms can not play the role of exotic matters which are crucial to form a traversable wormhole, and external exotic sources are still needed. In particular, the exotic matter behaves like phantom energy if Kehagias-Sfetsos vacuum is considered outside the wormhole. Interestingly, the spherically symmetric setting makes the matter and the higher curvature contribution satisfy four-dimensional conservation of energy in the covariant form.Comment: 13 pages, 2 figures, version published in Phys. Rev.

Drastic Reduction of Shot Noise in Semiconductor Superlattices

We have found experimentally that the shot noise of the tunneling current $I$ through an undoped semiconductor superlattice is reduced with respect to the Poissonian noise value $2eI$, and that the noise approaches 1/3 of that value in superlattices whose quantum wells are strongly coupled. On the other hand, when the coupling is weak or when a strong electric field is applied to the superlattice the noise becomes Poissonian. Although our results are qualitatively consistent with existing theories for one-dimensional mulitple barriers, the theories cannot account for the dependence of the noise on superlattice parameters that we have observed.Comment: 4 Pages, 3Figure

Axial anomaly and magnetism of nuclear and quark matter

We consider the response of the QCD ground state at finite baryon density to a strong magnetic field B. We point out the dominant role played by the coupling of neutral Goldstone bosons, such as pi^0, to the magnetic field via the axial triangle anomaly. We show that, in vacuum, above a value of B ~ m_pi^2/e, a metastable object appears - the pi^0 domain wall. Because of the axial anomaly, the wall carries a baryon number surface density proportional to B. As a result, for B ~ 10^{19} G a stack of parallel pi^0 domain walls is energetically more favorable than nuclear matter at the same density. Similarly, at higher densities, somewhat weaker magnetic fields of order B ~ 10^{17}-10^{18} G transform the color-superconducting ground state of QCD into new phases containing stacks of axial isoscalar (eta or eta') domain walls. We also show that a quark-matter state known as ``Goldstone current state,'' in which a gradient of a Goldstone field is spontaneously generated, is ferromagnetic due to the axial anomaly. We estimate the size of the fields created by such a state in a typical neutron star to be of order 10^{14}-10^{15} G.Comment: 18 pages, v2: added a discussion of the energy cost of neutralizing the domain wall charg

Two non-commutative parameters and regular cosmological phase transition in the semi-classical dilaton cosmology

We study cosmological phase transitions from modified equations of motion by introducing two non-commutative parameters in the Poisson brackets, which describes the initial- and future-singularity-free phase transition in the soluble semi-classical dilaton gravity with a non-vanishing cosmological constant. Accelerated expansion and decelerated expansion corresponding to the FRW phase appear alternatively, and then it ends up with the second accelerated expansion. The final stage of the universe approaches the flat spacetime independent of the initial state of the curvature scalar as long as the product of the two non-commutative parameters is less than one. Finally, we show that the initial-singularity-free condition is related to the second accelerated expansion of the universe.Comment: 13 pages, 4 figures; v2. to appear in Mod. Phys. Lett.

Generic Bell inequalities for multipartite arbitrary dimensional systems

We present generic Bell inequalities for multipartite multi-dimensional systems. The inequalities that any local realistic theories must obey are violated by quantum mechanics for even-dimensional multipartite systems. A large set of variants are shown to naturally emerge from the generic Bell inequalities. We discuss particular variants of Bell inequalities, that are violated for all the systems including odd-dimensional systems.Comment: Accepted in Phys. Rev. Let

Dirac quasinormal frequencies in Schwarzschild-AdS space-time

We investigate the quasinormal mode frequencies for the massless Dirac field in static four dimensional $AdS$ space-time. The separation of the Dirac equation is achieved for the first time in $AdS$ space. Besides the relevance that this calculation can have in the framework of the $AdS/CFT$ correspondence between M-theory on $AdS_4\times S^7$ and SU(N) super Yang-Mills theory on $M_3$, it also serves to fill in a gap in the literature, which has only been concerned with particles of integral spin $0,1,2$.Comment: 13 pages, 6 figure

Note on two-dimensional gauged Lifshitz models

We fermionize the two-dimensional free Lifshitz scalar field in order to identify what the gauge covariant couplings are, and then they are bosonized back to get the gauged Lifshitz scalar field theories. We show that they give the same physical modes with those of the corresponding Lorentz invariant gauged scalar theories, although the dispersion relations are different.Comment: 8 pages, to appear in MPL

Domain walls of high-density QCD

We show that in very dense quark matter there must exist metastable domain walls where the axial U(1) phase of the color-superconducting condensate changes by 2pi. The decay rate of the domain walls is exponentially suppressed and we compute it semiclassically. We give an estimate of the critical chemical potential above which our analysis is under theoretical control.Comment: 4 pages; Eq. (16) corrected, 2 new references added, published versio