0:00:04their work discrete body those and negative temperatures state
0:00:08has been done by stay final you being e
0:00:11a bad performance of the narrow band two d v
0:00:13don't work well but
0:00:15and then tanya quality
0:00:16in a collaboration among the universities of lawrence unitary state off glide in aberdeen in
0:00:23the united kingdom
0:00:24and the c in a incest of your in q no unique id
0:00:29first of all we want to clarify the meaning of negative temperatures
0:00:34by considering an is somewhat of to level up tones
0:00:37where the total internal energy is bound
0:00:40in the middle energy state all the atoms are in the ground state
0:00:45since this state is perfectly or that it's entropy zero
0:00:49but so is the entropy for the maximum energy state
0:00:53well all the atoms and in the excited state
0:00:57this means that if we plot of the entropy s as a function of the
0:01:01internal energy you we obtain a curve with at least one maximum value
0:01:07since the temperature t is the inverse of the slope of these curve we observe
0:01:12on the left side of the pitch or positive slope corresponding proposed a temperature
0:01:18and the maximum f zero slope when we have you think temperature
0:01:22and on the right of the pitch or negative slopes and negative temperatures
0:01:27this means the negative temperatures at extremely hot
0:01:30and the ball the temperature point
0:01:33this does not in anyway violated the absolute zero temperature is sorta
0:01:38i introduced by a lot caving
0:01:41in this paper we study negative temperatures states
0:01:44in the discrete can only enough shutting in equation
0:01:47this equation describes accurately both i think on the state you need the optical at
0:01:53these but also racial couple optical waveguide
0:01:57they helping to describe i the tunnelling effect of the b c in the optical
0:02:02at this or the coupling among the wave guides
0:02:06it is important to note that in the discrete can only initiating an equation
0:02:10that out to course of quantities the total energy and the total atomic density
0:02:17it is possible to provide a statistical mechanics description
0:02:21all the solutions of the discrete only the shouldn't get equation
0:02:25as displayed in this diagram would we report to the energy density verse of the
0:02:30part versus the particle density
0:02:32there exist a line of you think temperature unified
0:02:36separating a region of negative temperatures from a legion at positive temperatures
0:02:41the main question addressed in our work ease
0:02:44can we access the region at negative temperatures
0:02:50on that i we see the temporal evolution of two different realizations involved a pretty
0:02:56temperature line
0:02:57in both cases we observe the formation and then take elation
0:03:01of discrete body this that a highly spatially localized states corresponding to large values of
0:03:07the particle density in just if you laugh decides
0:03:11by increasing the size of the lack this aim we also observe that the density
0:03:16of body there's approaches require the stationary value corresponding to any terribly the distance of
0:03:22around nine hundred lap decides
0:03:28the presence of many discrete body thus in the quasi-stationary state and negative temperature is
0:03:34displayed in this animation
0:03:42there being the this the role approaches the final value that is independent of the
0:03:46initial condition and so that as the inverse of the temperature be to
0:03:51that converges the was negative values measured by suitable michael canonical thermometer
0:03:59it is possible in the discrete non linear fitting in equation to move from positive
0:04:03to negative temperatures
0:04:05without of the features changes of the sign of the energy
0:04:09by following a method introduced by some of us in two thousand and seeks one
0:04:13can remove particle and energy of the boundaries of the last is
0:04:18in progressively more across the line of v thingy temperatures
0:04:22in conclusion we have demonstrated
0:04:24the negative temperatures states with discrete readers should be experimentally realizable in b c in
0:04:31optical laugh theses and large arrays of optical waveguide
0:04:35it is possible to move from positive to negative temperatures but if the expansion of
0:04:40the b c
0:04:42on a large overlap this or by removing particles and energy from the boundary
0:04:47these methods do not rely on artificial changes of the sign of the total energy
0:04:53simply marloes