Gravity Modification with Yukawa-type Potential: Dark Matter and Mirror Gravity

The nature of the gravitational interaction between ordinary and dark matter is still open. Any deviation from universality or the Newtonian law also modifies the standard assumption of collisionless dark matter. On the other hand, obtaining a Yukawa-like large-distance modification of the gravitational potential is a nontrivial problem, that has so far eluded a consistent realization even at linearized level. We propose here a theory providing a Yukawa-like potential, by coupling non-derivatively the two metric fields related respectively to the visible and dark matter sectors, in the context of massive gravity theories where the local Lorentz invariance is broken by the different coexisting backgrounds. This gives rise to the appropriate mass pattern in the gravitational sector, producing a healthy theory with the Yukawa potential. Our results are of a special relevance in the scenario of dark matter originated from the mirror world, an exact duplicate of the ordinary particle sector.Comment: 19 page

Spacetime and vacuum as seen from Moscow

An extended text of the talk given at the conference ``2001: A Spacetime Odyssey'', to be published in the Proceedings of the Inaugural Conference of the Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, 21-25 May 2001, M.J. Duff and J.T. Liu eds., World Scientific, Singapore, 2002; and of Historical Lecture ``Vacuum as seen from Moscow'' at the CERN Summer School, 10 August, 2001. Contents: Introduction; Pomeranchuk on vacuum; Landau on parity, P, and combined parity, CP; Search and discovery of $K_L^0 \to \pi^+ \pi^-$; "Mirror world"; Zeldovich and cosmological term; QCD vacuum condensates; Sakharov and baryonic asymmetry of the universe, BAU; Kirzhnits and phase transitions; Vacuum domain walls; Monopoles, strings, instantons, and sphalerons; False vacuum; Inflation; Brane and Bulk; Acknowledgments; References.Comment: 17 pages, 2 figure

The proton spin sum rule chiral bag prediction, an update

We reevaluate a quark model prediction using the new QCD evolution function calculated to the 3 loop order and conclude that this model compares favorably with the new experimental results.Comment: 10 pages, 2 figures available by request, give fax numbe

Towards a unique formula for neutrino oscillations in vacuum

We show that all correct results obtained by applying quantum field theory to neutrino oscillations can be understood in terms of a single oscillation formula. In particular, the model proposed by Grimus and Stockinger is shown to be a subcase of the model proposed by Giunti, Kim and Lee, while the new oscillation formulas proposed by Ioannisian and Pilaftsis and by Shtanov are disproved. We derive an oscillation formula without making any relativistic assumption and taking into account the dispersion, so that the result is valid for both neutrinos and mesons. This unification gives a stronger phenomenological basis to the neutrino oscillation formula. We also prove that the coherence length can be increased without bound by more accurate energy measurements. Finally, we insist on the wave packet interpretation of the quantum field treatments of oscillations.Comment: 30 pages, 1 figure; the proof that plane wave oscillations do no exist is extended to stationary models; the influence of dispersion is explained in more detail

A Gravitational Potential with Extra-dimensions and Spin Effects In Hadronic Reactions

The impact of the KK-modes in d-brane models of gravity with large compactification radii and TeV-scale quantum gravity on the hadronic potential at small impact parameters is examined. The effects of the gravitational hadronic form factors obtained from the generalized parton distributions (GPDs) on the behavior of the gravitational potential and the possible spin correlation effects are also analysed.Comment: 13 pages, 7 figure

Geophysical constraints on mirror matter within the Earth

We have performed a detailed investigation of geophysical constraints on the possible admixture of mirror matter inside the Earth. On the basis of the Preliminary Reference Earth Model (PREM) -- the `Standard Model' of the Earth's interior -- we have developed a method which allows one to compute changes in various quantities characterising the Earth (mass, moment of inertia, normal mode frequencies etc.)due to the presence of mirror matter. As a result we have been able to obtain for the first time the direct upper bounds on the possible concentration of the mirror matter in the Earth. In terms of the ratio of the mirror mass to the Earth mass a conservative upper bound is $3.8\times 10^{-3}$. We then analysed possible mechanisms (such as lunar and solar tidal forces, meteorite impacts and earthquakes) of exciting mirror matter oscillations around the Earth centre. Such oscillations could manifest themselves through global variations of the gravitational acceleration at the Earth's surface. We conclude that such variations are too small to be observed. Our results are valid for other types of hypothetical matter coupled to ordinary matter by gravitation only (e.g. the shadow matter of superstring theories).Comment: 25 pages, in RevTeX, to appear in Phys.Rev.

Gravitomagnetic Effects in the Propagation of Electromagnetic Waves in Variable Gravitational Fields of Arbitrary-Moving and Spinning Bodies

Propagation of light in the gravitational field of self-gravitating spinning bodies moving with arbitrary velocities is discussed. The gravitational field is assumed to be "weak" everywhere. Equations of motion of a light ray are solved in the first post-Minkowskian approximation that is linear with respect to the universal gravitational constant $G$. We do not restrict ourselves with the approximation of gravitational lens so that the solution of light geodesics is applicable for arbitrary locations of source of light and observer. This formalism is applied for studying corrections to the Shapiro time delay in binary pulsars caused by the rotation of pulsar and its companion. We also derive the correction to the light deflection angle caused by rotation of gravitating bodies in the solar system (Sun, planets) or a gravitational lens. The gravitational shift of frequency due to the combined translational and rotational motions of light-ray-deflecting bodies is analyzed as well. We give a general derivation of the formula describing the relativistic rotation of the plane of polarization of electromagnetic waves (Skrotskii effect). This formula is valid for arbitrary translational and rotational motion of gravitating bodies and greatly extends the results of previous researchers. Finally, we discuss the Skrotskii effect for gravitational waves emitted by localized sources such as a binary system. The theoretical results of this paper can be applied for studying various relativistic effects in microarcsecond space astrometry and developing corresponding algorithms for data processing in space astrometric missions such as FAME, SIM, and GAIA.Comment: 36 pages, 1 figure, submitted to Phys. Rev.

More about neutron - mirror neutron oscillation

It was pointed out recently that oscillation of the neutron $n$ into mirror neutron $n'$, a sterile twin of the neutron with exactly the same mass, could be a very fast process with the the baryon number violation, even faster than the neutron decay itself. This process is sensitive to the magnetic fields and it could be observed by comparing the neutron lose rates in the UCN storage chambers for different magnetic backgrounds. We calculate the probability of $n-n'$ oscillation in the case when a mirror magnetic field $\vec{B}'$ is non-zero and show that in this case it can be suppressed or resonantly enhanced by applying the ordinary magnetic field $\vec{B}$, depending on its strength and on its orientation with respect to $\vec{B}'$. The recent experimental data, under this hypothesis, still allow the $n-n'$ oscillation time order 1 s or even smaller. Moreover, they indicate that the neutron losses are sensitive to the orientation of the magnetic field. %at about $3\sigma$ level. If these hints will be confirmed in the future experiments, this would point to the presence of the mirror magnetic field on the Earth of the order of 0.1 G, or some equivalent spin-dependent force of the other origin that makes a difference between the neutron and mirror neutron states.Comment: 10 page

Jet-quenching of the rotating heavy meson in a N{\mathcal{N}}=4 SYM plasma in presence of a constant electric field

In this paper, we consider a rotating heavy quark-antiquark ($q\bar{q}$) pair in a ${\mathcal{N}}$=4 SYM thermal plasma. We assume that $q\bar{q}$ center of mass moves at the speed $v$ and furthermore they rotate around the center of mass. We use the AdS/CFT correspondence and consider the effect of external electromagnetic field on the motion of the rotating meson. Then we calculate the jet-quenching parameter corresponding to the rotating meson in the constant electric field