24 research outputs found
Quantum Universe on Extremely Small Space-time Scales
The semiclassical approach to the quantum geometrodynamical model is used for the description of the properties of the Universe on extremely small space-time scales. Under this approach, the matter in the Universe has two components of the quantum nature which behave as antigravitating fluids. The first component does not vanish in the limit ħ → 0 and can be associated with dark energy. The second component is described by an extremely rigid equation of state and goes to zero after the transition to large space-time scales. On small space-time scales, this quantum correction turns out to be significant. It determines the geometry of the Universe near the initial cosmological singularity point. This geometry is conformal to a unit four-sphere embedded in a five-dimensional Euclidean flat space. During the consequent expansion of the Universe, when reaching the post-Planck era, the geometry of the Universe changes into that conformal to a unit four-hyperboloid in a five-dimensional Lorentz-signatured flat space. This agrees with the hypothesis about the possible change of geometry after the origin of the expanding Universe from the region near the initial singularity point. The origin of the Universe can be interpreted as a quantum transition of the system from a region in the phase space forbidden for the classical motion, but where a trajectory in imaginary time exists, into a region, where the equations of motion have the solution which describes the evolution of the Universe in real time. Near the boundary between two regions, from the side of real time, the Universe undergoes almost an exponential expansion which passes smoothly into the expansion under the action of radiation dominating over matter which is described by the standard cosmological model.Квазiкласичний пiдхiд до квантово-геометродинамiчної моделi застосовано для опису властивостей всесвiту на екстремально малих просторово-часових масштабах. У цьому пiдходi матерiя у всесвiтi має двi компоненти квантової природи, якi поводять себе як антигравiтуючi рiдини. Перша компонента не набуває нульового значення в границi ħ → 0 та може бути асоцiйована з темною енергiєю. Друга компонента описується екстремально жорстким рiвнянням стану i прямує до нуля пiсля переходу до великих просторово-часових масштабiв. На малих просторовочасових масштабах ця квантова поправка вiдiграє значну роль. Вона визначає геометрiю всесвiту бiля точки початкової космологiчної сингулярностi. Ця геометрiя є конформною до одиничної 4-сфери, зануреної у 5-вимiрний евклiдовий плоский простiр. Пiд час наступного розширення всесвiту, пiсля досягнення пост-планкiвської ери, геометрiя всесвiту перетворюється на геометрiю, конформну до одиничного 4-гiперболоїда у 5- вимiрному плоскому просторi з лоренцiвською сигнатурою. Це узгоджується з гiпотезою про можливу змiну геометрiї пiсля виникнення всесвiту, що розширюється з областi поблизу точки початкової сингулярностi. Виникнення всесвiту може бути iнтерпретовано як квантовий перехiд системи з областi у фазовому просторi, забороненої для класичного руху, але де iснує траєкторiя в уявному часi, в область, де рiвняння руху мають розв’язок, що описує еволюцiю всесвiту у реальному часi. Поблизу межi мiж двома областями, з боку реального часу, всесвiт зазнає майже експоненцiального розширення, яке гладко переходить у розширення пiд дiєю випромiнювання, що домiнує над матерiєю, у вiдповiдностi iз стандартною космологiчною моделлю
Wave function of the Universe in the early stage of its evolution
In quantum cosmological models, constructed in the framework of
Friedmann-Robertson-Walker metrics, a nucleation of the Universe with its
further expansion is described as a tunneling transition through an effective
barrier between regions with small and large values of the scale factor at
non-zero (or zero) energy. The approach for describing this tunneling consists
of constructing a wave function satisfying an appropriate boundary condition.
There are various ways for defining the boundary condition that lead to
different estimates of the barrier penetrability and the tunneling time.
In order to describe the escape from the tunneling region as accurately as
possible and to construct the total wave function on the basis of its two
partial solutions unambiguously, we use the tunneling boundary condition that
the total wave function must represent only the outgoing wave at the point of
escape from the barrier, where the following definition for the wave is
introduced: the wave is represented by the wave function whose modulus changes
minimally under a variation of the scale factor . We construct a new method
for a direct non-semiclassical calculation of the total stationary wave
function of the Universe, analyze the behavior of this wave function in the
tunneling region, near the escape point and in the asymptotic region, and
estimate the barrier penetrability. We observe oscillations of modulus of wave
function in the external region starting from the turning point which decrease
with increasing of and which are not shown in semiclassical calculations.
The period of such an oscillation decreases uniformly with increasing and
can be used as a fully quantum dynamical characteristic of the expansion of the
Universe.Comment: 19 pages, 21 files for 10 EPS figures, LaTeX svjour style. The Sec.2
(formalism of Wheeler-De Witt equation) is reduced. In Sec.3.1 definition of
the outgoing wave from barrier is defined more accurately. In Sec.4.1
semiclassical calculations of wavew function and penetrability are performed
and comparison with results in fully quantum approach is adde
Registration of atmospheric neutrinos with the Baikal neutrino telescope
We present first neutrino induced events observed with a deep underwater
neutrino telescope. Data from 70 days effective life time of the BAIKAL
prototype telescope NT-96 have been analyzed with two different methods. With
the standard track reconstruction method, 9 clear upward muon candidates have
been identified, in good agreement with 8.7 events expected from Monte Carlo
calculations for atmospheric neutrinos. The second analysis is tailored to
muons coming from close to the opposite zenith. It yields 4 events, compared to
3.5 from Monte Carlo expectations. From this we derive a 90 % upper flux limit
of 1.1 * 10^-13 cm^-2 sec^-1 for muons in excess of those expected from
atmospheric neutrinos with zenith angle > 150 degrees and energy > 10GeV.Comment: 20 pages, 11 figure
Three nucleon interaction in a quark cluster model
SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Three-body calculation of deuteron-nucleus Coulomb field interaction
SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman