Quote from: SeeShells on 06/27/2015 05:25 pmOne other thought that keeps popping in and out and how the evanescent momentum and spin vectors of the wave interacting with the Quantum Vacuum virtually homogeneous ZPF is it will no longer be homogeneous due to the everanscent's wave actions on it. It will literally warp the area of space 1/3 of the wavelength (where evanescent waves form) of the microwave harmonics from the frustum and...This corresponds to my "feeling/imagination" actually, but unfortunately I cannot form a theory either. I also feel that if nothing is spewing out then there must some kind of rotation, so I keep thinking of a helical disturbance to the truncated cone; in your design that would be like giving your pyramid a twist perhaps.
One other thought that keeps popping in and out and how the evanescent momentum and spin vectors of the wave interacting with the Quantum Vacuum virtually homogeneous ZPF is it will no longer be homogeneous due to the everanscent's wave actions on it. It will literally warp the area of space 1/3 of the wavelength (where evanescent waves form) of the microwave harmonics from the frustum and...
There's a lot of fractal in the data and in the pictures that Aero's produced. If whatever makes this happen is more 'ratchety' instead of linear, then that makes a lot of sense. ...The debate between Dr. Rodal and TheTraveller (get well soon) feels like a debate on how long a coastline is; it depends on if you use a meter stick or micrometer. ...
Quote from: Rodal on 06/26/2015 06:44 pmQuote from: aero on 06/26/2015 06:35 pmI don't recall whether or not I've posted this video, so here it is. I was fooling around back in April trying to create evanescent waves when I came across this very unusual pattern. I don't know that evanescent waves are involved at all but something unusual is showing up. You tell me? Superluminal velocity? Well, strange things do happen.Yes, in the acoustic analogue, this would be tantamount to shock waves due to exit speeds faster than the speed of sound. The shock waves would look like that.Wow! That's cool and relevant. One of the issues I've been having is the phase velocity > c inside the cone, so what happens when it exists the big end? I think this video just showed me what happens.Thank you.Todd
Quote from: aero on 06/26/2015 06:35 pmI don't recall whether or not I've posted this video, so here it is. I was fooling around back in April trying to create evanescent waves when I came across this very unusual pattern. I don't know that evanescent waves are involved at all but something unusual is showing up. You tell me? Superluminal velocity? Well, strange things do happen.Yes, in the acoustic analogue, this would be tantamount to shock waves due to exit speeds faster than the speed of sound. The shock waves would look like that.
I don't recall whether or not I've posted this video, so here it is. I was fooling around back in April trying to create evanescent waves when I came across this very unusual pattern. I don't know that evanescent waves are involved at all but something unusual is showing up. You tell me? Superluminal velocity? Well, strange things do happen.
...Forgive the awkwardness of this question, but don't I recall that phase velocity can be >c,...
Quote from: sghill on 06/27/2015 07:49 pm...Forgive the awkwardness of this question, but don't I recall that phase velocity can be >c,...Todd is correct, the phase velocity is greater than c for electromagnetic fields
Quote from: Rodal on 06/27/2015 07:53 pmQuote from: sghill on 06/27/2015 07:49 pm...Forgive the awkwardness of this question, but don't I recall that phase velocity can be >c,...Todd is correct, the phase velocity is greater than c for electromagnetic fieldsThat's what I said. I think you reversed the order of "don't I..." which would change my meaning. So, with that in mind, to reiterate again for a few of the naysayers that have popped up from time to time, we're not getting ANY information out of the >c phase velocity- just momentum. Therefore we are NOT talking about a time machine or "window into the past" as some have snorted about derisively on the thread.
Phase velocity is the velocity of waves that have well-defined wavelengths, and it often varies as a function of the wavelength. One can combine ("superpose") waves of different wavelengths to build a wave packet, a blob of some specified extent over which the wave disturbance is not small. This packet does not have a well-defined wavelength, and because it usually spreads out as it travels, it doesn't have a well-defined velocity either; but it does have representative velocity, and this is called its group velocity, which will usually be less than c. Each of the packet's constituent wave trains travels with its own individual phase velocity, which in some instances will be greater than c. But it is only possible to send information with such a wave packet at the group velocity (the velocity of the blob), so the phase velocity is yet another example of a speed faster than light that cannot carry a message. In some situations, we can build a fairly exotic wave packet whose group velocity is greater than c. Does this then constitute an example of information being sent at a speed faster than light? It turns out that for these packets, information does not travel at the group velocity; instead, it travels at the signal velocity, which has to do with the time of arrival of the initial rise of the wave front as it reaches its destination. You might not now be surprised to learn that the signal velocity turns out always to be less than c.
Quote from: sghill on 06/27/2015 08:01 pmQuote from: Rodal on 06/27/2015 07:53 pmQuote from: sghill on 06/27/2015 07:49 pm...Forgive the awkwardness of this question, but don't I recall that phase velocity can be >c,...Todd is correct, the phase velocity is greater than c for electromagnetic fieldsThat's what I said. I think you reversed the order of "don't I..." which would change my meaning. So, with that in mind, to reiterate again for a few of the naysayers that have popped up from time to time, we're not getting ANY information out of the >c phase velocity- just momentum. Therefore we are NOT talking about a time machine or "window into the past" as some have snorted about derisively on the thread.No, the discussion about the group velocity > c is also correct. The FTL effect for the group velocity is associated with the quantum tunneling effect of the evanescent waves.Electromagnetic fields inside a hollow cylindrical waveguide: phase velocity > c and group velocity < 0Evanescent waves quantum tunneling: phase velocity < c and group velocity > 0See the big change that occurs from inside the cavity to the outside of the cavity, this is what Todd is addressing.As I previously discussed, there is NO way to transmit information using the FTL group velocity tunneling of evanescent waves.We also have:phase velocity = c / n group velocity = c / (n + ∂n/∂ω)where n is the refractive index and ω = 2 * Pi * frequency .As I previously discussed the associations of information and momentum with group or phase velocity always have a context. Sorry ladies and gents, one is not going to make sense out of this without going through equations.
Uploading of 18x312 views of 9 inch cavity complete. Top level folder dated June 26, link is:https://drive.google.com/folderview?id=0B1XizxEfB23tfmcxbUxsM0lVTGVkemVTX1RaMlZJb001NHVaUDRvYUtjS0lIbjdIcUNkX0k&usp=sharingEnjoy.
Quote from: rfcavity on 06/26/2015 10:14 pmQuote from: WarpTech on 06/26/2015 09:53 pmRegarding resonant modes in the frustum. Would there still be resonant modes if;1. the frustum were open on the big end only?2. the frustum were open on both ends?IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?If it's closed at the small end, it should still support odd harmonics of p modes. Correct?Thank you!ToddIt would support TExx modes but they would be travelling, out the end of the device. It wouldn't be a energy store like normal closed cavities, but simply an antenna.https://en.wikipedia.org/wiki/Horn_antennaIs it possible in a cylinder (not a cone) to have a TExx mode that does not travel? It just resonates at one particular spot in the cylinder? Since this resonant mode is radial, not axial, I don't see why it would have any reason to move in either direction. c is in the radial direction. v in the axial direction should be 0.Todd
Quote from: WarpTech on 06/26/2015 09:53 pmRegarding resonant modes in the frustum. Would there still be resonant modes if;1. the frustum were open on the big end only?2. the frustum were open on both ends?IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?If it's closed at the small end, it should still support odd harmonics of p modes. Correct?Thank you!ToddIt would support TExx modes but they would be travelling, out the end of the device. It wouldn't be a energy store like normal closed cavities, but simply an antenna.https://en.wikipedia.org/wiki/Horn_antenna
Regarding resonant modes in the frustum. Would there still be resonant modes if;1. the frustum were open on the big end only?2. the frustum were open on both ends?IF I understand these modes correctly, the TExx0 modes resonate with the pointing vector radial in/out-ward from the axis to the walls. It seems to me, that a cone that is open on both ends would still support the same TEnm modes, just not the p modes. Correct?If it's closed at the small end, it should still support odd harmonics of p modes. Correct?Thank you!Todd
Thanks. I have considered the issue of max/min changing from image to image with and across the views. h5topng does have a switch to use the same max/min value within a data set but that leaves two problems.1 - The Max/Min values automatically chosen are invariably from the later cycles, because the power increases as the cavity starts to resonate strongly. That means the first 100 - 200 images within a view are nearly always featureless with perhaps the antenna showing. Not very useful for showing start-up transients.2 - As there are 18 data sets, there would still be 18 max/min ranges, so we still couldn't compare values between data sets anyway.Still, if we didn't need to see the complete evolution, I could run and plot only the final 1 or 2 cycles (10 - 20 images). This would reduce the upload time to a reasonable value and make the Max/Min range across the data set sufficiently uniform to justify plotting with fixed Max/Min values, per data set. That would also make the task of reducing the data with MatLab to show the RSS of the E and H field components a lot less unwieldy.The above doesn't consider the transfer of the raw data across the Internet. That is intractable with the full set of raw data as it requires 8 hours to upload one raw data field component as it stands now. That's 48 hours to upload all of the raw data, not to mention the time required to download same. Using only one full cycle should reduce that time to below 2 hours which becomes workable. Of course using only a single time point from each field component would make it quick. The question becomes, "Which time point?" so it seems that, "Use one full cycle," is the best answer.
...So, what happens when you have a short Horn antenna with a really bad impedance mismatch at the open end? Waves are reflected at the opening, but there is no material there to absorb the recoil. Correct? So could we still be able to establish resonance at the TE011 mode, using the VSWR as the p-mode? In other words, the reflecting surface is the vacuum. Or am I missing something again?Todd
Quote from: WarpTech on 06/27/2015 09:51 pm...So, what happens when you have a short Horn antenna with a really bad impedance mismatch at the open end? Waves are reflected at the opening, but there is no material there to absorb the recoil. Correct? So could we still be able to establish resonance at the TE011 mode, using the VSWR as the p-mode? In other words, the reflecting surface is the vacuum. Or am I missing something again?ToddThe classical issue of SWR is due to mismatch between a load impedance (the antenna) and the transmission line. The standing wave takes place in the feed line and not in the antenna (as part of the forward wave sent toward the load (the antenna) is reflected back along the transmission line towards the source). The antenna acts a a resistive load. The impedance mismatch is between the antenna and the feed line, instead of between the antenna and the vacuum. The standing wave is formed in the feed line instead of getting formed in the antenna.My understanding is that there's no mismatch with the vacuum or with air because the vacuum or air are not resistive loads and therefore there is no need to match their impedance. Impedance mismatch implies that energy is reflected somehow. But if you hook your 50 Ohm source up to a 50 Ohm antenna (that is sitting in air) you will see a VSWR=1, or no reflection. The power radiates away, and there is no spot for reflection (or impedance mismatch) to occur. JR calling Notsosureofit: ring, ring, ring. Notsosureofit knows much more about this than I do, so I look forward to Notsosureofit's comments regarding impedance mismatch between a microwave antenna and the vacuum and standing waves produced in the antenna as a result of this impedance mismatch.
Quote from: aero on 06/27/2015 10:10 pmThanks. I have considered the issue of max/min changing from image to image with and across the views. h5topng does have a switch to use the same max/min value within a data set but that leaves two problems.1 - The Max/Min values automatically chosen are invariably from the later cycles, because the power increases as the cavity starts to resonate strongly. That means the first 100 - 200 images within a view are nearly always featureless with perhaps the antenna showing. Not very useful for showing start-up transients.2 - As there are 18 data sets, there would still be 18 max/min ranges, so we still couldn't compare values between data sets anyway.Still, if we didn't need to see the complete evolution, I could run and plot only the final 1 or 2 cycles (10 - 20 images). This would reduce the upload time to a reasonable value and make the Max/Min range across the data set sufficiently uniform to justify plotting with fixed Max/Min values, per data set. That would also make the task of reducing the data with MatLab to show the RSS of the E and H field components a lot less unwieldy.The above doesn't consider the transfer of the raw data across the Internet. That is intractable with the full set of raw data as it requires 8 hours to upload one raw data field component as it stands now. That's 48 hours to upload all of the raw data, not to mention the time required to download same. Using only one full cycle should reduce that time to below 2 hours which becomes workable. Of course using only a single time point from each field component would make it quick. The question becomes, "Which time point?" so it seems that, "Use one full cycle," is the best answer.I definitely (No doubt about it) prefer to use the feature that: <<h5topng does have a switch to use the same max/min value within a data set but that leaves two problems.1 - The Max/Min values automatically chosen are invariably from the later cycles, because the power increases as the cavity starts to resonate strongly. That means the first 100 - 200 images within a view are nearly always featureless with perhaps the antenna showing. Not very useful for showing start-up transients.>>That's PERFECT.A number of readers of this thread unfamilar with FD methods are getting the WRONG impression that the field is fractal and that the transient is important.If the transient is negligible (as expected) and the fractal nature is an artifact of the FD method plotting very small values that are physically zero, so much the better.The FD method cannot exactly satisfy the boundary conditions so you never get a perfect zero, you get a very small value. Much better to plot it as a zero, particularly when people in this thread are getting confused.Yes no doubt about it, from now on: << switch to use the same max/min value within a data >>Concerning comparing values between different data sets, MEEP allows you to output NUMERICAL values (the old fashioned way). You could output some numerical values for the very LAST time step at one of the particular data sets, to ascertain the numerical relationship between the data sets.
Given a direction constant, and a meep::volume*, returns the flux (the integral of \Re [\mathbf{E}^* \times \mathbf{H}]) in that volume.
...Would this QuoteGiven a direction constant, and a meep::volume*, returns the flux (the integral of \Re [\mathbf{E}^* \times \mathbf{H}]) in that volume. be a useful data point? I believe it is saying Real {E* x H}here: http://ab-initio.mit.edu/wiki/index.php/Meep_Reference#Field_computationsMaybe you will see other output features there that you like. I can see if my version of meep is current enough to use them.
Quote from: aero on 06/28/2015 12:00 am...Would this QuoteGiven a direction constant, and a meep::volume*, returns the flux (the integral of \Re [\mathbf{E}^* \times \mathbf{H}]) in that volume. be a useful data point? I believe it is saying Real {E* x H}here: http://ab-initio.mit.edu/wiki/index.php/Meep_Reference#Field_computationsMaybe you will see other output features there that you like. I can see if my version of meep is current enough to use them.Oh, yes, definitely !!!That's the Poynting vector , that 1) would get around the issues of having to deal with components; and 2) would show the energy flux, the Poynting vector, which is what everybody is interested in---------------NOTE: It looks to me that you excited TE212. I base this on the strong axial magnetic component, showing p=2. The problem is that the resonant frequency of TE212 is only 1.89954 GHz. TE213 is much closer to 2.45 GHz frequency, since TE213 has 2.38836 GHz frequency, but TE213 implies p=3 and I only see p=2 in the magnetic mode.I recall that you said that you put the antenna to excite an electric mode, that is consistent with exciting TE212. An idea would be to run everything the same, (L=9 inches) but with the antenna set to excite a magnetic mode, to see whether you excite TM212 at 2.45 GHz or so.
Quote from: Rodal on 06/27/2015 10:56 pmQuote from: WarpTech on 06/27/2015 09:51 pm...So, what happens when you have a short Horn antenna with a really bad impedance mismatch at the open end? Waves are reflected at the opening, but there is no material there to absorb the recoil. Correct? So could we still be able to establish resonance at the TE011 mode, using the VSWR as the p-mode? In other words, the reflecting surface is the vacuum. Or am I missing something again?ToddThe classical issue of SWR is due to mismatch between a load impedance (the antenna) and the transmission line. The standing wave takes place in the feed line and not in the antenna (as part of the forward wave sent toward the load (the antenna) is reflected back along the transmission line towards the source). The antenna acts a a resistive load. The impedance mismatch is between the antenna and the feed line, instead of between the antenna and the vacuum. The standing wave is formed in the feed line instead of getting formed in the antenna.My understanding is that there's no mismatch with the vacuum or with air because the vacuum or air are not resistive loads and therefore there is no need to match their impedance. Impedance mismatch implies that energy is reflected somehow. But if you hook your 50 Ohm source up to a 50 Ohm antenna (that is sitting in air) you will see a VSWR=1, or no reflection. The power radiates away, and there is no spot for reflection (or impedance mismatch) to occur. JR calling Notsosureofit: ring, ring, ring. Notsosureofit knows much more about this than I do, so I look forward to Notsosureofit's comments regarding impedance mismatch between a microwave antenna and the vacuum and standing waves produced in the antenna as a result of this impedance mismatch.Boy, that's going way back. Seems we always looked at an antenna as a matching transformer between the line and the impedance of free space. (the antennas on sounding rockets, we would try to match or measure the ionosphere) Anyway, the reaction momentum would be to the last free carrier that acted as the radiation oscillator. Goes back to Plank, I believe.