The Inconsistency Puzzle Resolved: an Omitted Variable

The contemporary version of the dynamic Ramsey problem omits expectations of a household’s initial lump-sum wealth taxation due to policy revision; therefore, the attainable resource allocation set in this problem is ill-defined. This omission leads to misleading conclusions about the optimal policy in the short run and, in particular, that the Ramsey policy is dynamically inconsistent. The effect of introducing the expectations into the analysis of dynamic inconsistency is similar to that of introducing expected inflation into the Phillips curve: we show that only an unexpected policy surprise affects the attainable resource allocation set and the optimal policy. In contrast to Chamley (1986), we show that intensive capital income taxation at the beginning of an optimal policy does not imply a lump-sum taxation of household wealth and cannot reduce the excess tax burden. We also demonstrate that the Ramsey policy is dynamically consistent even without commitment. We resolve the Ramsey problem and compare our results to those of Chamley on optimal capital income taxation.Consistency, Equilibrium policy, Optimal taxation

Assessment of the Investment Appeal of Hydropower Construction Based on the Analytic Hierarchy Process

The purpose of the paper is description of the method of estimating the investment appeal rate of hydropower construction in the federal subjects. The method is based on Analytic Hierarchy Process (AHP). According to the method every federal subject is estimated by the decision-maker. The authors collected data for this study from Russian Federal State Statistics Service, the Federal Subjects Development Programs and the Power Industry Development Programs of the federal subjects (23 indicators). The federal subjects were estimated according to these indicators. As a result of this project every estimated federal subject has status: attractive, relatively attractive and non-attractive for hydropower development. The results can be applied to calculate the economic hydropower potential. The method was tested for detecting the attractive federal subjects of the Volga Federal District, North Caucasian Federal District, Northwestern Federal District, Siberian Federal District for hydropower development

Electron confinement by laser-driven azimuthal magnetic fields during direct laser acceleration

A laser-driven azimuthal plasma magnetic field is known to facilitate electron energy gain from the irradiating laser pulse. The enhancement is due to changes in the orientation between the laser electric field and electron velocity caused by magnetic field deflections. Transverse electron confinement is critical for realizing this concept experimentally. We find that the phase velocity of the laser pulse has a profound impact on the transverse size of electron trajectories. The transverse size remains constant below a threshold energy that depends on the degree of the superluminosity and it increases with the electron energy above the threshold. This increase can cause electron losses in tightly focused laser pulses. We show using 3D particle-in-cell simulations that the electron energy gain can be significantly increased by increasing laser power at fixed intensity due to the increased electron confinement. This finding makes a strong case for designing experiments at multi-PW laser facilities

Quantum anti-quenching of radiation from laser-driven structured plasma channels

We demonstrate that in the interaction of a high-power laser pulse with a structured solid-density plasma-channel, clear quantum signatures of stochastic radiation emission manifest, disclosing a novel avenue to studying the quantized nature of photon emission. In contrast to earlier findings we observe that the total radiated energy for very short interaction times, achieved by studying thin plasma channel targets, is significantly larger in a quantum radiation model as compared to a calculation including classical radiation reaction, i.e., we observe quantum anti-quenching. By means of a detailed analytical analysis and a refined test particle model, corroborated by a full kinetic plasma simulation, we demonstrate that this counter-intuitive behavior is due to the constant supply of energy to the setup through the driving laser. We comment on an experimental realization of the proposed setup, feasible at upcoming high-intensity laser facilities, since the required thin targets can be manufactured and the driving laser pulses provided with existing technology.Comment: 6 pages, 3 figure

Enhancement of laser-driven electron acceleration in an ion channel

A long laser beam propagating through an underdense plasma produces a positively charged ion channel by expelling plasma electrons in the transverse direction. We consider the dynamics of a test electron in a resulting two-dimensional channel under the action of the laser field and the transverse electric field of the channel. A considerable enhancement of the axial momentum can be achieved in this case via amplification of betatron oscillations. It is shown that the oscillations can be parametrically amplified when the betatron frequency, which increases with the wave amplitude, becomes comparable to the frequency of its modulations. The modulations are caused by non-inertial (accelerated/decelerated) relativistic axial motion induced by the wave regardless of the angle between the laser electric field and the field of the channel. We have performed a parameter scan for a wide range of wave amplitudes and ion densities and we have found that, for a given density, there is a well pronounced wave amplitude threshold above which the maximum electron energy is considerably enhanced. We have also calculated a time-integrated electron spectrum produced by an ensemble of electrons with a spread in the initial transverse momentum. The numerical results show that the considerable energy enhancement is accompanied by spectrum broadening. The presented mechanism of energy enhancement is robust with respect to an axial increase of ion density, because it relies on a threshold phenomenon rather than on a narrow linear resonance