1,843 research outputs found
On the Power Spectrum Density of Gamma Ray Bursts
Gamma ray bursts (GRBs) are known to have short-time variability and
power-law behavior with the index -1.67 in the power spectrum density.
Reanalyzing the expanded data, we have found a) the power-law comes from the
global profile of the burst and not from the self-similar shots nor rapid
fluctuations in the luminosity profile. b) The power indices vary from burst to
burst and the value -1.67 is given simply as the mean value of the
distribution; there is no systematic correlation among GRBs to yield the power
law.Comment: 10 pages, 4 figures, submitted to ApJ Letter
NMR relaxation of quantum spin chains in magnetic fields
We investigate NMR relaxation rates 1/T_1 of quantum spin chains in magnetic
fields. Universal properties for the divergence behavior of 1/T_1 are obtained
in the Tomonaga-Luttinger-liquid state. The results are discussed in comparison
with experimental results.Comment: 5 pages, 3 figure
森林管理インセンティブプログラムに経済的インセンティブは本当に有効か? 久万林業活性化プロジェクトの再契約に関する私有林所有者の意思決定を事例とした検証
近年、私有林における森林保全や持続可能な林業を目指した自発的インセンティブプログラムが注目を集めている。欧米では、私有林所有者のプログラムへの参加行動に関する研究が盛んに行われている。プログラム参加者の再契約行動を理解することは、長期的な保全や持続的な管理を達成するために重要である。しかしながら、再契約行動に関する研究は世界的に数少ない。そこで本論文では、再契約行動に関する理論分析と、愛媛県久万高原町における「久万林業活性化プロジェクト」の契約者データを用いた計量分析を行った。その結果、契約期間中に森林の共同管理が実際に実施された契約者の方が、再契約する確率が高くなることが示された
The Random Bit Complexity of Mobile Robots Scattering
We consider the problem of scattering robots in a two dimensional
continuous space. As this problem is impossible to solve in a deterministic
manner, all solutions must be probabilistic. We investigate the amount of
randomness (that is, the number of random bits used by the robots) that is
required to achieve scattering. We first prove that random bits are
necessary to scatter robots in any setting. Also, we give a sufficient
condition for a scattering algorithm to be random bit optimal. As it turns out
that previous solutions for scattering satisfy our condition, they are hence
proved random bit optimal for the scattering problem. Then, we investigate the
time complexity of scattering when strong multiplicity detection is not
available. We prove that such algorithms cannot converge in constant time in
the general case and in rounds for random bits optimal
scattering algorithms. However, we present a family of scattering algorithms
that converge as fast as needed without using multiplicity detection. Also, we
put forward a specific protocol of this family that is random bit optimal ( random bits are used) and time optimal ( rounds are used).
This improves the time complexity of previous results in the same setting by a
factor. Aside from characterizing the random bit complexity of mobile
robot scattering, our study also closes its time complexity gap with and
without strong multiplicity detection (that is, time complexity is only
achievable when strong multiplicity detection is available, and it is possible
to approach it as needed otherwise)
Rendezvous of Two Robots with Constant Memory
We study the impact that persistent memory has on the classical rendezvous
problem of two mobile computational entities, called robots, in the plane. It
is well known that, without additional assumptions, rendezvous is impossible if
the entities are oblivious (i.e., have no persistent memory) even if the system
is semi-synchronous (SSynch). It has been recently shown that rendezvous is
possible even if the system is asynchronous (ASynch) if each robot is endowed
with O(1) bits of persistent memory, can transmit O(1) bits in each cycle, and
can remember (i.e., can persistently store) the last received transmission.
This setting is overly powerful.
In this paper we weaken that setting in two different ways: (1) by
maintaining the O(1) bits of persistent memory but removing the communication
capabilities; and (2) by maintaining the O(1) transmission capability and the
ability to remember the last received transmission, but removing the ability of
an agent to remember its previous activities. We call the former setting
finite-state (FState) and the latter finite-communication (FComm). Note that,
even though its use is very different, in both settings, the amount of
persistent memory of a robot is constant.
We investigate the rendezvous problem in these two weaker settings. We model
both settings as a system of robots endowed with visible lights: in FState, a
robot can only see its own light, while in FComm a robot can only see the other
robot's light. We prove, among other things, that finite-state robots can
rendezvous in SSynch, and that finite-communication robots are able to
rendezvous even in ASynch. All proofs are constructive: in each setting, we
present a protocol that allows the two robots to rendezvous in finite time.Comment: 18 pages, 3 figure
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